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Household Surveys, Trip Purposes, and Travel Time

Sherman Lewis, Professor EmeritusCalifornia State University East Bay, Hayward2787 Hillcrest Ave.Hayward CA 94542510-538-3692Sherman@csuhayward.us

AbstractAdvocates of walkable neighborhoods believe they can provide mobility equal to or better

than suburbia. This idea is, however, difficult to test quantitatively. The paper examines data from four large household survey databases in order to establish travel time budgets based on the frequency and travel times for 15 trip purposes. The problematic purposes of “vehicle per se” and “serve passenger” are discussed. Trips by seniors and children, long trips, and home round trips are discussed. Typical behavior establishes travel time budgets for a full range of trip purposes as a basis for evaluating and improving the performance of walkable neighborhood systems. Several topics for future work are suggested: analysis of data from the California Household Travel Survey for round trips, improving definitions of trip purposes, and improving walkable neighborhoods.

1 IntroductionNeighborhood systems can be compared in many ways, one of which looks at how well

they meet different travel needs. Mobility is the ability to get where one wants to go in an acceptable travel time and cost. Accessibility is the flip side of mobility emphasizing the closeness of the places one wants to go to. Mobility gets to places that are accessible. Mobility emphasizes movement; accessibility emphasizes land use and proximity. Mobility is getting to the places we want to go, and accessibility is getting to the places we want to go. For an example of an emphasis on access, Krizek’s Neighborhood Access (NA) (Krizek, 2003) examines the availability of land uses meeting daily errands. His concern is to reduce VMT, while the concern here is walkable neighborhoods.

Mokhtarian and Chen (2004) review many studies of travel time budgets and conclude that “Travel time expenditure is strongly related to individual and household characteristics (e.g., income level, gender, employment status, and car ownership), attributes of activities at the destination (e.g., activity group and activity duration), and characteristics of residential areas (e.g., density, spatial structure, and level of service).… [F]urther research into explaining travel time and money expenditure patterns is justified.”

Neighborhood systems are defined by the land use, transportation, and their costs in the market. They range along a density spectrum from rural to exurban, suburban, central city, and urban core. Walkable neighborhoods are a type of urban core system with medium density (50 to 100 persons per walkable acre), mid-rise average building height (three to seven stories), restricted vehicle use, attractive walking distances, and density over area to support local

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business and frequent transit efficiently. A walkable neighborhood system is denser than a central city or street car system, but less dense than a high-rise system, which is over about 100 persons per walkable acre. In a walkable neighborhood fewer than 40 percent of trips are by auto. (Vehicle and auto are used here interchangeably to mean a personal vehicle, but not to mean carshare/rental.)

The walkable neighborhood is denser and less car dependent than smart growth, which is usually central city density and subsidizes ample parking.

Walkable neighborhoods planned for the future can achieve a very high level of sustainability. Some existing historic neighborhoods near old downtowns do not reach as high a level but still achieve much more sustainability than suburbia. Walkable neighborhoods clearly outperform suburbia on non-auto modes, Vehicle Miles Traveled (VMT), fossil fuel use, greenhouse gases (GHG), air quality, and accidents.

Existing travel times for many purposes, which are not normative as such, can be used as a basis for comparing different kinds of neighborhood systems. Since suburbia dominates household survey data, it sets a base line of mostly auto travel times to evaluate non-auto travel times in a walkable neighborhood.

The paper focuses on what the travel times are, not why they are, so variables explaining travel behavior are not studied. Looking just at travel times and purposes also simplifies the analysis and makes it easier to deal with large databases.

Mobility research has several goals. Walkable neighborhood mobility can be studied quantitatively to test the general belief among urbanists that such neighborhoods have mobility equal to or better than suburbia. There is also the contrasting concern among suburbanites, how can we get there without a car? Detailed information on trip times can be used to educate people about how mobility works in a walkable neighborhood. Mobility research can be used as a basis for deparking policies and other mobility improvements in existing walkable neighborhoods, which in turn, would help their overall mobility and sustainability. “Many planning efforts aim to develop neighborhoods with higher levels of accessibility that will allow residents to shop closer to home and drive fewer miles.” (Krizek, 2001) Better estimates of trips in planned walkable neighborhoods can improve the ability of models to predict their VMT, GHG, air quality and energy improvements.

3 TerminologyMobility is measured in terms of travel time budgets for fifteen different purposes of

travel, using survey data to define the budgets. “Acceptable” travel time may involve different kinds of thinking, in some cases minimizing, in other cases optimizing, in some cases involving considerable thought, in other cases, no thought at all.

There are several contexts for travel budget decisions. One context is the locational decision about where to live or work. For example, employed people decide where to live based on the amount of travel time they are willing to spend to get to work. They may have to live some distance from work to find housing, but if the travel time and related costs become too great, they can’t take the jobs. A locational decision may involve optimizing among travel time to work, quality and affordability of a house and neighborhood, and closeness to good schools.

Another context is short routine trips. People are usually willing to spend a large amount

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of time getting to work but a small amount of time on errands. As people live in a place, they learn more about available destinations and become more efficient in trip chaining. They look for closer stores and restaurants rather than ones that are farther away. They may adjust their time of travel to avoid congestion or accumulate errands to save travel time.

Travel time budgets have little or no effect on infrequent trips, which may require long distance travel to a specific event, or which may involve searching out an accessible place for an infrequent purpose.

Mode of travel cuts both ways, with each mode having its own specific pros and cons. Walking sometimes has negatives of personal safety, need for physical effort, carrying things, exposure to weather, and distance. However, walking also has positives, like the low cost, physical activity, health benefits, scenic enjoyment, and social interaction.

Cycling has issues like the cumbersomeness of managing and storing the bicycle. Pavements may be rough, hills are challenging to climb, and carrying things may be difficult. Vehicle traffic can be especially threatening to cyclists. However, bicycling can also be healthy, fun, much faster than walking, and often advantageous to go medium distances quickly.

While transit has negatives of wait time and slowness, it too has positives. The research shows that people are willing to spend more time on transit than driving because it avoids bridge tolls, parking charges, and other auto expenses. Also, transit is less stressful, and allows reading, some kinds of work, and resting. There is variation within the transit category also, with high quality rail attracting more riders than city buses. BART, for example, becomes very competitive when the rider does not have to own, but high fares can also deter ridership. Low fares for city buses attract riders, but they tend to be slow.

The auto is expensive to purchase, insure, maintain, and manage (vehicle per se, i.e., the vehicle as such, discussed below), but the low price of gasoline makes for a low marginal cost. Sometimes congestion, tolls, and parking charges discourage trips, while free flow, freeways, and “free” parking encourage them.

Litman 2014) says “Under favorable conditions, walking, cycling and public transit travel can have relatively low costs per minute or hour, since walking and cycling can be enjoyable activities that substitute for special time dedicated to exercise, and if they are comfortable, public transit passenger can rest or work, which is not possible for drivers. As a result, many commuters are willing to accept a longer duration commute by walking, cycling or public transit.”

4 Personal home-based round tripsHome-based round trips start and end at a home in a neighborhood, take place within a

day, have one or more destinations along the way, and do not involve more than six hours of travel time. Most people, in fact, spend much less time traveling. During an average day, a person spends one hour and 25 minutes traveling.1 All of the trips of Table 1 below are parts of home round trips. Overnight trips are excluded because they do not take place within a day.

Note that this definition is different from traditional transportation analysis. For example, home-based trips include one from an exercise activity to a grocery store, while in traditional analysis it would be called a non-home based trip.

Personal trips are those which meet personal and household needs rather than those of a

1 American Time Use Survey, cited in Database list

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business or other non-household entity. Work-based trips, for work purposes or to and from work clearly do not count as personal.

A trip is travel from an origin to a destination to achieve a purpose at the destination. All travel is not necessarily a trip. In some cases, as discussed by Mokhtarian and Solomon (2001), travel may be its own activity, not a trip to get to a destination. They distinguish three utilities for traveling. One is the need to engage in the activity, like work or shopping, at the destination in the context of some expectation about travel time. The second is activities like relaxing, reading, or conversing while traveling. The third utility is “undirected travel” desired for its own sake, for “a sense of speed, motion, control, enjoyment of beauty…” Examples are walking the dog, which is an activity, not a trip. (Travel in order to walk the dog would be a trip.) Similarly, travel for pleasure is an activity, an end in itself, not a trip. Traveling ten minutes in order to jog is a trip, while jogging itself is not a trip. Neighborhood mobility focuses on getting to destinations, with the other utilities being less important.

The mobility of a neighborhood is its ability to support personal home-based trips for all its residents. A relatively minor trip purpose for some can be a frequent trip for others, so trip purposes are broadly inclusive. Neighborhoods include people with many different purposes, all of which contribute to the mobility of the area and help evaluate its performance.

Trip purposes do not include going home. Going home is not a purpose, but rather an integral part of the destination purpose. With a direct trip to and from a purpose, all the time for the two trips is assigned to the purpose. If two or more destinations are involved, the time needs to be split up in some way among the purposes.

Travel time includes all stages of a trip, where a stage is a mode of travel, such as walk, bike, drive, ride, and even wait time, in various combinations. Travel time is not precisely defined by the surveys, but does include the various stages of a trip, not just the driving time. It is not clear if the surveys include the time from the front door to the auto and from the auto to the entry of the destination activity. Such walks at the end of an auto trip can add a minute or more to travel time, giving the walkable neighborhood more time to compete. (One minute of pure walking covers about the length of a football field. Comparative mobility requires contrasting similar travel times in a context of very different travel distances.)

Some trips are part of a neighborhood, while others are part of the mobility of a distant location. A distant major activity may include side trips related to the activity, not the home. These side trips, such as going out to lunch during work or to a place close to the destination, are part of the destination mobility system.

Routine trips are the most important for evaluating mobility. They are predictable and frequent, as contrasted with unusual trips, which are infrequent, unpredictable, or long in time and distance.

A purpose taking 30 minutes to two hours (sources vary) is a major destination, major activity, or anchor purpose. Longer routine trips to a major activity are very important for the mobility of a neighborhood. The longer trip typically involves going to work, education, or a frequent social commitment like babysitting that a person needs to reach in an acceptable travel time. For these trips, the neighborhood has to have that mobility for a resident to be willing to live there. If major destinations change, a family may move to a location better meeting those needs.

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5 Data Until recently, computer modeling has typically used very simplified trip purposes, mainly

home-based work, home-based shopping/personal business, home-based social/recreational, and non-home-based. While adequate for projecting traffic flows on highway networks, the list is too simple for the complexity of neighborhood mobility. Fortunately, a vast amount of data on many trip purposes is available in household surveys.

Four recent large household travel surveys have data on many trip purposes and how long they take. The surveys are the American Time Use Survey (ATUS, 2012), the National Household Travel Survey (NHTS, 2009), the California Household Transportation Survey (CHTS, 2011), and the Metropolitan Transportation Commission Bay Area Transportation Survey (BATS, 2000). They overlap to a great extent, but use varying definitions. Data from the four surveys was compiled on a master spreadsheet leading to Table 1. (Lewis, 2015)

American Time Use Survey The ATUS (2012) reported all uses of time for one day adding up to 24 hours. Most time is

activity in a place; some time is travel time related to reach the activity. The ATUS lexicon is a rich source of examples of activities and specific trips. The ATUS has 23 useful trip purposes. Travel time in the ATUS combined the time of trips with the same purpose in one day into one time, while the other surveys all reported single trip times.

The ATUS is useful for total time spent traveling, average travel time for the US population, and average time for those making a particular trip. Travel time of those doing an activity was spread to the whole population. Travel times which were short for the whole population were larger for the smaller number of people who actually made the trips.

With one exception, the ATUS assigned travel time to the destination purpose of the travel, such as to work, education, or shopping. The exception was the trip home, for which the time was assigned to last destination before home, and added to the time to reach the last destination. Thus, some trips have extra time assigned because the trip home is included.

Table 2 from the ATUS has detailed travel time by purpose for the whole day, not just a trip. The travel time in a day is generally the result of two trips, so the trip time in the master spreadsheet for ATUS data is half its reported total time. (Lewis, 2015)

National Household Travel SurveyThe NHTS (2009) has detail on trip making and a web utility supporting making tables with

up to three variables. It used 27 useful trip purposes. The NHTS database, DAYV2PUB, was analyzed for average, median, and standard deviation for 27 trip purposes. The database has special large datasets for multi-stop round trips.

Bay Area Transportation Survey (BATS) 2000In 2000 The Metropolitan Transportation Commission of the San Francisco Bay Area

surveyed many respondents on their travel (BATS, 2000). The Bay Area Transportation Survey covered the nine counties of the Bay Area. It had trip data for 19,502 household days. BATS had some travel time data, in one case on all trips in five-minute increments, and in another case on five broad categories of trips which do not reveal most trip purposes. “Home-based work” and “Home-based education” are clear enough, but “Home-based shop and other” and “Home-based social recreational” included too many different purposes to be meaningful for this research. “Non-home based” trips has no specific purpose information; they included all trips

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for all purposes that do not have home at either end.2 The BATS also had some detail on a longer list of types from which ten purposes could be derived. The BATS did not report travel time for detailed purposes and therefor was used less than the other surveys.

California Household Transportation SurveyThe CHTS Bay Area, a subset of the whole CHTS (2011), is available online. The San

Francisco Bay Area Metropolitan Transportation Commission (MTC) was a major participant in the CHTS research. Caltrans oversampled the Bay Area to update the BATS survey of 2000 to get the statistical validity MTC needed. The CHTS has high quality data from using GPS reporting from devices carried around by the respondents. The CHTS surveyed 42,431 households. The CHTS used 17 purposes similar to the NHTS. Of the four surveys, the California Household Transportation Survey is used the most because it uses the best methodology. The CHTS data is the most sophisticated because of its use of three different GPS devices: wearable, in vehicle, and in vehicle with an on-board diagnostic unit.

Methodological issuesStandard deviation and purposeComparison of mobility among neighborhood systems needs to use median time, which is

the experience of the middle person or average person answering the question, with half of the other respondents taking less time and half taking more. Average time is longer because of the way longer times of some respondents pull the average time above the median. Standard deviation measures how much data is dispersed or concentrated around a middle value. Dispersed data has a large deviation, in the case of trips due to many trips being longer than the median. A graph for time shows a long tail to the right with longer and fewer trips.

The household surveys sometimes combine trips of a different character into single trip purposes. This problem is most evident when there is a large standard deviation for an apparent single purpose which hides functionally different purposes.3 For example, banking trips need to be split between an errand trip to an ATM and a trip to apply for a loan. Trips to see a lawyer or real estate agent are infrequent but get lumped in with short trips for more

2 BATS has 21 types of records with no time data: 10 are trip purposes, 5 are not trips (changed mode, other, don’t know, refused, and unknown). 6 are in the home (home, household chores, sleep, shopping at home, relaxing/ resting, and non-work,-shop internet). The 21 types are in an OD (Origin – Destination) table, including going from sleep to sleep. The 5 not trips were deleted. The 6 in-home types were combined. The OD table then had 10 trip purposes: Meals Away, Recreation/Entertainment, Work or Work Related, School or School Related, Shop away from home, Pers. Serv./Bank/Gov't, Social Activities, Vol./Civic/Religious, Sick/Ill/Medical Appt., and Serve Passengers. They were added to the master spreadsheet.3 Many standard deviations are bigger than the mean, indicating great variation in travel time. In the NHTS the standard deviation as a percent of the median ranged from 87 percent to 125 percent. Work trips, oddly enough, had only an 88 percent deviation, due to a high base number. The biggest variations in time were for serve passengers (125 percent), Family personal business/obligations (123 percent), coffee/ice cream/snacks (123 percent), attend funeral/wedding (121 percent), buy gas (121 percent), and day care (121 percent). Where median time is short, the longer trips are still short, but a longer median may indicate different purposes combined into one.

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common services. Longer special trips could form one category despite disparate purposes: real estate, insurance, finance, legal, governmental, etc.

Similarly, errand trips for different purposes, particularly weekly and convenience shopping, have similarly short travel times, and are distinct from special shopping and services. For these errand trips, the distinction between trips to get goods and trips to get services is not helpful. For example, The CHTS reported 13.5 minutes for routine shopping and 12.9 for household errands, too similar in time to matter. Table 1 below combines these two purposes.

Trip purpose, activity, placeTrips need to be distinguished from activities. The NHTS and CHTS were not always clear if

the numbers were about an activity and how long it took, or about a trip to the activity and how long the trip took.

Sometimes data were not clear if they dealt with a trip purpose, an activity, or a place. Home, for example, is a place, and sleep is an activity. Sleep is reported as a trip purpose without revealing the place where the activity, in this case inactivity, occurs. The surveys do not reveal the origin for the trip to the sleep destination. CHTS Final Report p. 115 Table 8.3.1, for example, has eight trip purposes that take place at home, implying many trips within the home. However, sleep is at-home activity and thus not a trip purpose. Routinely going somewhere else to sleep would be odd: one would have to leave home for the purpose of sleeping and not be on an overnight trip.

The master spreadsheet (Lewis, 2015) excluded many CHTS trips that did not seem to be trips: going to the eight activities in the home; “Change type of transportation/transfer (walk to bus, walk to/from parked car);” and “Other (specify), Loop trip, don’t know/refused.” Almost half the trips were excluded, leaving 17 useful trip purposes.

“Personal care” is another example. Personal care refers to personal bathing and hair care and this category is not counted for trips because its activities take place in the home. However, trips to have someone else do it, like a haircut, counts as a trip with a different term for the trip purpose: personal care service trip. Sometimes a trip purpose is reported as personal care without revealing the location or differentiating between personal care and personal care service. Many of these trips are likely to be actually a trip home, where the activity takes place. People generally do not leave home to do personal care and come back home again. In many cases the surveys report trips to activities without revealing that almost all of them take place in the home. Trips that seemed to go to activities that take place predominantly in the home were excluded. This reduction, however, considerably reduces the number of total trips and travel time per day.

Trivial trip typesA few kinds of travel are too trivial to report. An example of a trivial trip is the ATUS

reported travel related to making telephone calls, which is very small in total trip time, and also 24th of the 25 trip purposes. Not only are these trips small in number, they are diminishing due to cell phones. Also, the destination is not a purpose. The purpose relates to the purpose of the call; people don’t travel to a telephone just to reach it. The ATUS lists dozens of trips statistically too few to have the numbers reported. In some cases, this reflects an over-proliferation of trip purposes, and some consolidation would result in more useful information.

Another example of “not a trip” comes from the ATUS, where the research ignored the real

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reason for travel. The ATUS reported “travel related to security procedures,” but in fact the traveler’s purpose is to get to work or get on an airplane, not the security procedure of going through a metal detector or something similar. Also, this travel is not significant, being the 25th of 25 purposes.

6 Data analysis and findings6.1 Trip purposes

Trip purposes were abstracted from the four databases into the master spreadsheet, Household Surveys and Travel Time Budgets. (Lewis, 2015). The ATUS had 23 useful categories, the NHTS had 27, the CHTS had 17, and BATS had 10. The Summary 3 page combines all the surveys by trip purpose, showing travel time, rank, and source of the data and is the basis for Table 1. Few purposes were consistent among surveys, so the combined list was difficult to construct. Generally, trip purposes that were infrequent or are narrowly defined did not line up with other data. The ATUS had the most prolific list of purposes, which made it more possible to relate its findings to other studies.

All purposes were straightforward but two, which are discussed below. Serve passenger“Serve passenger,” also called chauffeured trips, is a person taking others to a destination

or going to a destination to pick them up. Serve passenger is a trip purpose in the NHTS, CHTS, and BATS surveys. The NHTS even divided this trip into four purposes: pick up someone, drop someone off (these two are biggest), transport someone, and take someone and wait (these two are quite small). Serve passenger excludes trips made by drivers who are paid to carry passengers, like taxi drivers and transit drivers.

The “serve passenger” trip is problematic because it is not a real purpose, which is that of the passenger, such as to get to or from work or education. The surveys report the purpose for the passengers but not the driver. Ideally, serve passenger trips would be added to trips for the purpose of the passenger, but there is no way to do this, so they are counted even though not a true trip purpose. The surveys miss the real purpose of the trip.

The ATUS gets closer to a purpose for serve passenger by reporting travel related to “care for others.” The ATUS divides the time between household members and non-household members, between children and adults, between “caring for” vs. “helping,” and further still among purposes of health, education, and other. An overly complex matrix resulted in most categories too small to have reportable results. The ATUS provides details on caring for and helping activities, but skimps reporting on “travel related to” the activities, so the purpose and travel times are not clear.

The ATUS total time traveling to care for others was so much higher than the survey reports for serve passenger that it raised questions about whether they were only for “serve passenger.” The ATUS found 21.4 percent of the population active on an average day and spending 37 minutes traveling to care for others. Care for others was 12 percent of total travel time, much higher than the serve passenger figures from the other surveys, which were 9 percent, 8 percent, and 6 percent. It seems likely that the ATUS has more kinds of trips in addition to serve passenger, and it would be interesting to have more detail, given the importance of this trip. To be useful, these trips should be related to the purpose of the passenger, as education trips, health trips, and so on.

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“Serve passenger” is phrased in such a way that it means an auto trip with driver and passenger, but in the walkable neighborhood there would be analogous trips to serve someone by non-auto mode. These trip purposes are completely unrecognized in the surveys.

Vehicle per seThe “vehicle per se” trip is also problematic. Vehicle per se time is that needed to be able

to use an auto. Vehicle per se is not just the time to get to the gas station, but also the time to fill up and pay, which is an activity at the destination. Vehicle per se travel and activities include buying a car, registration, driver’s license, insurance, gas, tire changes, maintenance and oil changes, smog checks, repairs, accidents, and the aftermath of accidents. Vehicle per se even includes reading Consumer Reports about what auto to buy, vacuuming the interior, washing and waxing the exterior, managing snow chains, and cleaning the driveway.

Vehicle per se is not a true trip purpose, but rather a trip needed to use an auto for trips for real purposes. To apportion vehicle per se trips to the real purposes, they would have to be prorated to the purposes for which the auto is used, increasing their travel times.

Vehicle per se is not recognized as a trip and activity in support of other purposes, which seriously underreports a critical aspect of travel for purpose of analyzing neighborhood systems.

Given the importance of the concept, a special calculation was made. Relevant ATUS activity time was added to per se travel time to get total vehicle per se time. The base of all travel time was increased by the amount of per se activity time. The resulting total per se time was then estimated at 6.3 percent of total travel time, which would jump this purpose from eleventh up to seventh in total travel time in Table 1.4

While it may be less important, analogous per se costs for other modes are totally unreported—walking per se, biking per se, and transit per se.

Trip purposes and timesThe data from the four databases were organized in terms of trip purposes and times and

melded into a consensus shown in Table 1. What is the most important of the many purposes of travel? This question could not be

answered meaningfully because each purpose is important in its own way. “Total time traveling” is calculated as the number of trips of a given purpose multiplied by its average travel time and used to rank the trip purposes without claiming how important they might be.

In one category, “Social/visit friends/relatives”, the CHTS does not differentiate between informal socializing and special social trips. Table 1 shows an estimated split using ATUS and NHTS data into “informal socializing” and “special social trips.” While the CHTS is the main guide, the table rounds off the numbers and considers other sources.

4 Most vehicle per se trips are not reported or are buried in other categories. Trips for buying an auto and auto insurance, for example, are lumped in with special shopping and services. The CHTS reports some vehicle per se trips at 2.3 percent of trips and 17.5 minutes per trip. BATS folded everything into other categories, while both the ATUS and NHTS have buying gas as a trip. The ATUS has the best, if incomplete, information on this issue; travel time and activity time for purchasing gas and for maintaining an auto by oneself or by others.

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Table 1: Trip purposes by total travel timeTrip purposes by total travel time

FrequencyAverage trip time

Purpose per day minutes % rankWork and Work Related 0.315 23.0 22.6% 1Education 0.152 18.2 8.7% 4Meals away from home

Snacks, coffee, drive through, etc. 0.045 13.0 1.8% 14Eat meal at restaurant/diner 0.133 16.7 6.9% 5

Shopping and servicesroutine shopping and services 0.366 13.1 14.9% 2special shopping and services 0.070 17.3 3.8% 9

HealthHealth care 0.042 20.5 2.7% 13Outdoor exercise 0.077 17.9 4.3% 7Indoor exercise 0.038 15.2 1.8% 15

SocialCivic/religious activities 0.059 16.1 3.0% 12entertainment 0.049 24.5 3.7% 10informal socializing 0.096 21.6 6.5% 6special social trips 0.048 28.4 4.3% 8

Serve passengers / Care for others 0.265 13.5 11.2% 3Vehicle per se 0.062 19.3 3.7% 11

total 1.82 100% 15 purposesCHTS all surveys

Total travel time = number of trips times average travel time

Estimated total travel time

These purposes can be compared to Krizek’s ten purposes for Neighborhood Access. The NA analysis is not based on surveys and lacks data on travel time or frequency. The article is still useful because it focuses on mobility in neighborhoods and the competitiveness of denser neighborhoods (Krizek, 2003).Krizek travel purposes Household survey purposes1. Work Work and Work Related2. Personal (getting a service done or

completing a transaction, e.g. banking, gas station, dry cleaning)

Most is in routine shopping and services; gas station is in vehicle per se

3. Free-time (non-task oriented activities, e.g., entertainment, dining, theater, sports, church, clubs, library, exercise)

In 7 purposes: eat meal at restaurant, diner; four purposes under social trips; outdoor and indoor exercise

4. Convenience shopping (e.g., bread, milk), a corner store.

Part of routine shopping and services

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5. Comparison goods shopping (e.g., furniture, appliance, clothing)

Part of special shopping and services

6. Specialty goods shopping (e.g., niche markets, boutiques)

Part of special shopping and services

7. Appointment, e.g. doctor’s appointment, meeting

Some is in health care, some is in special shopping and services

8. Visiting (similar to free-time) Informal socializing9. School Part of education10. College Part of educationNot included Snacks, coffee, drive throughNot included Serve passengerGas station included with other purposes, otherwise not included

Vehicle per se

6.2 Seniors and childrenSeniors and children have special mobility patterns. Table 2 uses these general purposes:HBW – Home Based Work tripsHBSH – Home Based Shopping and personal business tripsHBSR – Home Based Social and Recreational tripsHBSC – Home Based School tripsNHB – Non-home Based trips

Table 2: Trips per day and for 5 general purposes by ageTrips per day and for 5 general purposes by ageAge Average Total Share of Trips by Trip PurposeGroup Trips/Person HBW HBSH HBSR HBSC NHB0-17 2.58 1.3% 22.6% 28.9% 29.9% 17.3% 100.0%18-39 3.16 25.9% 24.7% 20.4% 5.4% 23.7% 100.0%40-64 3.42 22.6% 30.7% 19.9% 1.5% 25.2% 100.0%65 + 2.73 5.9% 41.9% 28.8% 0.9% 22.5% 100.0%Condensed from Tables 412, 412E, 412F (BATS, 2000)

Table 3 has detail on family type but without trip purposes.

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Table 3: Life Cycle Category and NHTS and BATS number of households

NHTS 2001 Percent BATS 2000 PercentLife Cycle Category Households of Total Households Of TotalOne Adult, No Children 16,332,000 15.2 496,779 20.1Two or More Adults, No Children 22,458,000 20.9 563,135 22.8One Adult, Youngest Child 0-5 1,950,000 1.8 35,259 1.4Two or More Adults, Youngest Child 0-5 15,427,000 14.4 390,062 15.8One Adult, Youngest Child 6-15 3,058,000 2.8 81,759 3.3Two or More Adults, Youngest Child 6-15 15,016,000 14.0 388,345 15.7One Adult, Youngest Child 16-21 1,135,000 1.1 42,619 1.7Two or More Adults, Youngest Child 16-21 5,139,000 4.8 100,784 4.1One Adult, Retired, No Children 11,513,000 10.7 126,608 5.1Two or More Adults, Retired, No Children 15,308,000 14.3 240,670 9.8Unknown 30,000 0.0 0 0.0TOTAL 107,366,000 100.0 2,466,020 100.0NHTS Source: U.S. Department of Transportation, 2004. p. 99. BATS, 2000

Tables 2 and 3 can be used together.Seniors About 25 percent of the US population is retired with no children in the household (NHTS,

2009. Table 3). “[I]ndividual travel increases as people age from their early twenties to their mid-forties and then gradually decreases as individuals move into their senior years.” (BATS, 2000. p. 130) Trip making declines by 20 percent from the next youngest age group. Work and school trips shrink dramatically with a corresponding increase in shopping, personal business, social and recreational trips. Trips shift to part-time or part-year jobs, health care, babysitting, and long distance travel. The statistics do not differentiate among the healthy, the slow mobile, and the immobile. Loss of a driver’s license can affect travel and lead to relocation. A walkable neighborhood has inherent advantages for the physically less mobile, which require design to be realized.

Seniors are more flexible than workers about where to live. They may relocate close to family and to warmer, or less expensive, senior-supportive housing or retirement locations. So far, however, walkable neighborhoods have not had apparent special appeal for seniors. Yet a walkable neighborhood designed for senior needs could perform better than suburbia, if designed for health care and easy shopping.

Minor ChildrenHouseholds with children are almost 40 percent of all households. The surveys do not

cover trips with children as such. Children are very low in work trips and very high in school trips. Many serve passenger trips are likely to involve school trips.

The topic deserves some discussion outside the framework of travel time because most people do not know how to manage child trips without a car and because it is important for comparative mobility. Child transport from birth to age 5 requires using a child seat for a car, and from birth to toddlerhood it needs a stroller or carry sling. Often gear has to be carried. Once underway in a car travel is easy, but the same is true with a stroller. Both require hands-on steering.

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Travel gets easier with older children. They become self-loading into the vehicle and can walk. They still require a chauffeur, usually an unpaid volunteer, e.g., the parent.

Travel for children is more difficult than for adults, but there is no reason to think one neighborhood system is necessarily better than another, except that suburbia and cars are inherently more dangerous, especially for teenagers.

6.3 Long tripsThe CHTS is the only survey with a discussion of long trips, those over 50 miles, but it is not

clear how they related to other trips. Respondents prepared a special log going back two weeks as well as keeping a daily diary. The CHTS report on long distance trips combined the diary and the log. Some 25 percent of the total long distance trips are reported in the diary only or in both the diary and the log, with the remaining 75 percent of trips only in the log. Since the diary trips are included in the main statistics, they made travel times longer than otherwise.

The CHTS discussion of long trips used a different trip purposes. It included the usual trip purposes for work, work-related, education-related, visiting, etc., and added a new purpose, vacation/sightseeing. Ninety-four percent of these trips were for business or pleasure and the remainder for personal business, health care, and education. The long distance work trips averaged 171 miles while the work trip from the diary report is only 26 miles. It is not clear how much longer the commute in the main report is because of the inclusion of some long, non-routine work trips. The modes for long trips are also reported and included long auto trips, inter-city bus trips, cruises, intercity rail, and airplane trips.

Long trips in general are not related clearly to neighborhood system performance. They are generally not routine and are usually long in both time and distance, whether by car, plane or train. A few, however, may be long but frequent trips to work, education, or other major activity, and could be related to neighborhood system.

6.4 Home round trips“Home round trips” and “tours” as used here are synonymous. The household

transportation surveys focus on individual trips from one purpose to another, and not on how they may be part of a home round trip, which is the isolated trip approach. Krizek (2013) advocates the importance for neighborhoods of tour-based analysis as compared to single purpose trips.5 He defines tours as home round trips, while other sources include more kinds of tours. Home round trips are often influenced by how households coordinate trips among members.

5 Krizek (2013) discusses the literature on PDF p. 7. The literature has limited information on home round trips as defined narrowly here. It discusses the broader topic of chains and tours, and usually in the context of methods and models rather than an analysis of trip time by purpose using household surveys. A few discussions of chains or tours begin to look at the issue, but with a focus on quantitative methods, miles, modes, and descriptive data without attention to home round trips as such. Activity-based computer modeling is beginning to use tours, including home round trips. While San Diego still uses traditional four step models, which do not allow tours, it is developing activity-based model, which simulates transportation decisions for daily travel. See http://www.sandag.org/index.asp?subclassid=120&fuseaction=home.subclasshome.

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Home round trips or tours include one stop and multi-stop trips. Most home round trips are one stop trips, or direct trips to a destination and home again, also called simple tours or out and back. These trips dominate the survey data.

Home round trips with more than one stop are called chained trips and are of are of two types, those with a major destination activity with stops along the way (“I’ll stop on the way home”) and errands in a loop from home (“I’m going out on errands”).

Errand trips are particularly important for understanding mobility in neighborhood

A Google search for “NHTS trip chaining tours” does not find anything. Other articles similarly do not lend themselves to comparative evaluation of neighborhood systems. See Kevin Krizek, “Neighborhood Services, Trip Purpose, and Tour-Based Travel,” Transportation 30: Nov. 2003, pp. 387-410; Linda Kostyniuk et al., “Improving the Accuracy of Trip-Chaining Information in Activity/Travel Surveys, for an international conference in South Africa, Aug 5-11, 2001; Nancy McGuckin and Elaine Murakami, “Examining Trip-Chaining Behavior” by men and women, FHWA, and “Trips, Chains, and Tours, NHTS Conference, Nov. 1-2, 2004; Nancy McGuckin et al., “Trip-chaining trends in the U.S.,” Journal of the TRB 1917, Dec. 28, 2006; Christian Schneider et al., “Unraveling daily human mobility motifs, Journal of the Royal Society Interface, May 8, 2013; Frank Southworth, “Multi-destination, multi-purpose trip chaining…,” Papers of the Regional Science Association 57, 1985 (includes a summary of work to 1985).

Some common types of tours include stopping for coffee etc. on the way to work, serve passenger for education, stop to exercise/shop/eat or take out meal on way home, and errands only. One estimate for workers in 2001 found that 27 percent has one stop or more on their work trips. The major purposes from largest to smallest are Serve Passenger, Shop, Family and Personal Business, Meal/Coffee, Gas, and social/recreational. However, all trip purposes are found on tours, both to and from work.

Krizek’s article came closest to the topic of this paper. His definition of neighborhood accessibility (NA) is part of smart growth thinking. NA considers that neighborhoods typically have more workers than jobs, but do have many local businesses and free time destinations like dining, theater, sports, exercise, entertainment, church, clubs, and library. “Free time purposes” is a useful way of grouping diverse activities, distinct from local business and work and education. Krizek also used the shopping distinction of convenience, comparison, and specialty categories, with decreasing frequency, increasing distance, and more time. He invented the category of appointment for health care, but it applies to other services as well, with the most common often found in the neighborhood and more specialized services at a distance. He expected there to be elementary schools in the neighborhood. “Visiting” is hard to analyze due to the diversity of personal preferences. He found that high NA actually has less trip chaining, but more short trips. While their destinations are much more in the neighborhood than low NA places, high NA persons went outside for 80 percent of their errands.

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systems. The convenience of a car for errand trips among dispersed stops maybe hard to match in a walkable neighborhood. Travel time budgets are different for errand trips than for major activity trips. An urgent errand might precipitate a special trip, but often a person accumulates a bunch of errands before deciding they, combined, are worth the travel time. Having a number of errands close together reduces the time per errand to fit the travel time budget. A person knows travel times for major activities from the start because they are considered in the locational decision, while doing errands becomes more efficient over time as a person learns where things are.

A home round trip by walking depends on enough density over area to support local business to meet typical monthly needs. A fast, frequent, free shuttle to an area with local businesses could make the difference in having a competitive travel time. In general, it is advantageous to have many destinations clustered close together, as in a typical old downtown or in a new mega store.

NHTS on home round tripsThe NHTS (2009) has data sets on tours in addition to those on trips. NHTS defined tour as

a trip with stops between two anchor destinations, i.e., those with more than 30 minutes of activity. The data included travel time and the number of stops but not the purposes of the stops or the longest trip within the tour.6 Chart 1 below shows number of trips, travel time, and time per stop out to 7 stops. About 61 percent of trips have only one stop, so they are direct trips, with a median time of 28 minutes and an average time of 38 minutes. For all home round trips the median time is 30 minutes and the average time is 44 minutes.

6 C:\Users\HAPA\Dropbox\Mobility Analysis\NHTS Trip chaining\Trip chaining tour09 78864 rows V cols w analysis.xlsx. Records in tour files are more complex than those in trip files because they add columns for all the trips within the tour. The original data set was reduced for analysis and excludes OO, OW, WO and WW tours and has 130,112 records. Chart 1 covers 1 to 7 stops, which were 99.8 percent of reported trips (tours with 8 stops or more were rare).

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Chart 1: Home Round Trip Travel Time

1 2 3 4 5 6 70

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0

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Number of round trips

travel timetime per stop

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Num

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utes

of r

ound

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or p

er st

op

(NHTS 2009)With more stops the number of trips tapers off rapidly and tour time increases. However,

the time per errand decreases, showing increased efficiency with more errands. Two stop trips have about 26 percent of trips Taking out direct trips (1 stop) does not change the curve much, only two stop; trips dominate, with and a travel time only a little longer at 47 minutes, indicating the travel time increase for the second stop is 9 minutes, just short of half a mile walking.

The NHTS data also allowed some breakdown within the home based category.7 HH is a tour from home and back again without an anchor purpose away from home, implying an errands trip. The other tours had W for Work and O for Other along with the H, resulting in two

7 NHTS (2009) reduced data set C:\Users\HAPA\Dropbox\Mobility Analysis\NHTS Trip chaining\ DAYV2PUB main worksheet.xlsx. The high end time shown of 130 minutes in Chart 2 includes 97.3 percent of the two tour pairs and 99.9 percent of HH tours. Two tour pairs are 74 percent of the total and HH are 26 percent. The two tour pairs are about 253,000 and HH tours total about 90,000, for a total of 343,035 tour records. There is a discrepancy between the two spreadsheets, with DAYV2PUB showing 33.5 minutes average tour time and Trip chaining tour09 showing 44.2 minutes. The original NHTS (2009) data set, DAYV2PUB NHTS original.xlsx, has almost 500,000 records. To focus on home round trips, pairs that lacked the home were excluded.

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tour pairs of HO and OH and HW and WH.. The HH trip time is simple, combining the outbound time with the return to home time. The two tour pair trip time combined the two tours (out and back) into one time. These two tour pairs had significantly more travel time than the HH tours, indicating that W and O anchor purposes are associated with much longer travel times, shown in Chart 2.

Chart 2: Home-home and two tour pairs

0 10 20 30 40 50 60 70 80 90 100 110 120 1300

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8,854 7,035 5,938

2,809 2,464 2,778 1,083

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1,671 1,182 645 145 195

Home-home and two tour pairs, in 10 minute intervals

Two tour pairs

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0 10 20 30 40 50 60 70 80 90 100 110 120 1300

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8,854 7,035 5,938

2,809 2,464 2,778 1,083

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1,671 1,182 645 145 195

Home-home and two tour pairs, in 10 minute intervals

Two tour pairs

Home-Home

Minutes

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(NHTS, 2009)The two tour pairs averaged 41 minutes travel time and the HH tours, 14 minutes, but the

medians are more important and more telling: 30 minutes for two pair tours and 10 minutes for HH tours. Since the HH tour is the closest thing to an errands trip, the challenges for a walkable neighborhood is great. A five minute walk one way implies a walk distance of only a quarter of a mile. This distance recurs frequently in smart growth discussions as the easy distance, with other commentary supporting half a mile or a bit over for a doable distance. The challenge is to get enough density over that walkable area to support local business and transit.

The sample can be divided at the median to create a subsample of the longest travel time respondents. The average errand time for this long half is 21 minutes and the median is 15 minutes. The difference for walking is great; a 7.5 minute one way walk goes just short of .4 miles. These estimates give some sense of the planning parameters for a walkable neighborhood. While the errands trip is challenging, the two tour pair trips are far more common and far easier to achieve with enough density and non-auto modes.

Table 4 shows the distribution of trips for HH and for two tour pairs.8 The purposes shown

8 NHTS (2009) reduced data set C:\Users\HAPA\Dropbox\Mobility Analysis\NHTS Trip chaining\ DAYV2PUB main worksheet.xlsx. Table 4 uses the WHYTO coding; WHYFROM and WHYTRP1S

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are the ones consolidated above into table 1. The table also raises the question: how many trip purposes are enough? If four or five seems too simple, maybe 31 is too many. The surveys generally seem to reflect curiosity without a policy purpose. The table creates information overload not clearly related to walkable neighborhood mobility, yet also could be a starting point for a lengthy if tedious discussion for evaluating a walkable neighborhood.

For the two tour pairs, the top anchor purpose is work and work-related, with 23 percent of home round trips. Buy goods, in second place for two tour pairs, moves up to first place for home to home, with 33 percent of the HH total, supporting the notion that the HH trip is typically an errands trip.

Second place for HH, surprisingly, is serve passenger, with 19 percent of total HH trips. It seems likely that almost all of them are made by a person driving. It raises the question of how much these trips are necessitated by a dispersed suburban system and how comparable trips are made in the urban core. In the urban core there may be many fewer serve passenger trips because people would be walking and using transit short distances and not need to be served by someone else. If so, the walkable neighborhood system would perform better than suburbia on this issue. The major exception would be serving child travelers, also necessary in a walkable system.

The remaining top purposes for HH tours are more expected: go to gym, buy services, and pet care, with the rest under 5 percent. These purposes should be fairly easy to meet in a walkable neighborhood.

Table 4 gives an impression of how much errands are done on HH trips compared to two tour pairs. Categories 40 to 42 show more errands being done on two tour pairs than on HH tours. A walkable system which is long on the HH errand side could compensate by being competitive on errands that are part of the two tour pairs.

are not analyzed.

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Table 4: Distribution by purposeDistribution by purpose

# % rank % rank11 = Go to work 11 24,887 19.7% 1 0 0.0% 3012 = Return to work 12 1,318 1.0% 18 0 0.0% 3113 = Attend business meeting/trip 13 424 0.3% 27 29 0.1% 2914 = Other work related 14 2,340 1.9% 13 480 1.1% 1320 = School/religious activity 20 866 0.7% 23 85 0.2% 2521 = Go to school as student 21 9,165 7.3% 3 132 0.3% 2222 = Go to religious activity 22 7,988 6.3% 7 178 0.4% 2123 = Go to library: school related 23 169 0.1% 31 36 0.1% 2724 = OS - Day care 24 330 0.3% 30 36 0.1% 2830 = Medical/dental services 30 5,304 4.2% 9 1,089 2.4% 1040 = Shopping/errands 40 2,408 1.9% 12 2,146 4.8% 741 = Buy goods: groceries/clothing/ hardware store 41 14,029 11.1% 2 10,128 22.7% 142 = Buy services: video rentals/dry cleaner/post office/car service/bank 42 3,716 2.9% 11 4,069 9.1% 443 = Buy gas 43 1,821 1.4% 17 1,123 2.5% 950 = Social/recreational 50 2,123 1.7% 14 432 1.0% 1451 = Go to gym/exercise/play sports 51 8,120 6.4% 6 6,591 14.8% 352 = Rest or relaxation/vacation 52 913 0.7% 22 263 0.6% 1753 = Visit friends/relatives 53 8,935 7.1% 4 1,358 3.0% 854 = Go out/hang out: entertainment/ theater/sports event/go to bar 54 4,201 3.3% 10 253 0.6% 1955 = Visit public place: historical site/museum/ park/library 55 829 0.7% 24 278 0.6% 1660 = Family personal business/ obligations 60 2,013 1.6% 16 1,014 2.3% 1161 = Use professional services: attorney/accountant 61 464 0.4% 26 255 0.6% 1862 = Attend funeral/wedding 62 366 0.3% 28 43 0.1% 2663 = Use personal services: grooming/ haircut/nails 63 1,154 0.9% 20 331 0.7% 1564 = Pet care: walk the dog/vet visits 64 829 0.7% 25 2,871 6.4% 565 = Attend meeting: PTA/home owners association/ local government 65 1,297 1.0% 19 226 0.5% 2070 to 73 = Serve pasenger 70 - 73 7,769 6.2% 8 8,309 18.6% 280 = Meals 80 362 0.3% 29 95 0.2% 2481 = Social event 81 2,055 1.6% 15 104 0.2% 2382 = Get/eat meal 82 8,913 7.1% 5 2,166 4.9% 683 = Coffee/ice cream/snacks 83 1,068 0.8% 21 521 1.2% 12

126,176 100.0% 44,641 100.0%

Two tour pairs HH tours

NHTS 2009

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MTC on home round ripsThe BATS (2000) stated:

This table shows the propensity of workers and students to travel directly from home to work or school in the morning as opposed to driving directly home during the evening commute. … Therefore, the number of people traveling directly from home-to-work is 14.5 percent higher than those traveling directly from work-to-home. This reflects the increased willingness of individuals to make intermediate trips during the commute home (to stop at the grocery store or gym, or for a meal, etc.) as opposed to making these stops on the way to work or school.” (p. 13)

Approximately 28 percent of work-to-shop (other) trips are for trips from work to personal services such as banking, dry cleaning, or government services. Work-to-social/recreational trips are primarily made up of work-to-meal trips (70 percent), which typically represent midday work-to-lunch trips. Another major contributor to work-to-social/recreational trips is work-to-recreation/entertainment trips (16 percent). Since this category includes exercise, midday and post-work trips from work to the gym likely make up the plurality of work-to-recreation/entertainment trips. (p. 36)

MTC also had a draft file with Alameda County tours, which was analyzed in order to identify the purposes of stops on home round trips.9 To focus on stops, the major purposes of Work and University and School are omitted from the table below. Escort is eliminated as not being a trip purpose, but “discretionary” is included without definition. The table below shows the distribution of trip purposes of stops on tours, indicating the likelihood of such purposes being chained. This table uses some different and undefined trip purposes but provides more data on the purposes of chained trips.

9 MTC made progress on tour research, but not with a home round trip focus. MTC prepared large data files on tours which were difficult to use because of the size of the files, the number of data dictionaries, and the incompleteness of the dictionaries. MTC staff helped with some analysis of Alameda County. The tour file had nine trip purposes which were different from the trip file list used in MTC’s 2000 report. The new purpose terms were “university,” “escort” (probably serve passenger), maintenance, visiting, and “discretionary,” which were probably recasts of the original lists, but not correlated with them. The data had ten purpose columns: primary purpose, eight intermediate purposes (four out and four inbound), and joint purpose, which was not defined. Zero evidently meant there was no trip. The primary purpose column showed one of the nine trip purposes and the next columns more purposes if any, with more and more zeroes. The data allowed an analysis of the purposes of the tours.

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Table 5: Most frequent purposes of home-based round trips5. Shop 5 32%6. Maintenance 6 21%7. Eating Out 7 18%8. Visiting 8 7%9. Discretionary 9 21%all 100%

Source: S. Israel, email and telephone calls, November 2013 to July 2014

7 ConclusionsUse CHTS for home round trip analysisThe CHTS public use dataset could be analyzed for home round trips and the purposes of

their stops and major destinations.10 Errand destinations that are scattered in suburbia need to be concentrated to allow efficient trip chaining for errands by walking. Quantification would help evaluate and improve walkable neighborhoods.

Improve definitions of trip purposesThe data collected in household surveys could be improved by having a policy focus of

evaluating mobility in neighborhood systems. The several agencies should agree on a common list of purposes and definitions. A policy focus and better definitions would help bring the vehicle per se and serving passengers trips into focus, both to understand car dependency, most of which is ignored, and to understand analogous trips in walkable neighborhoods. The ATUS especially lends itself to combining activity and travel time, and with mode information could help with auto time and non-auto correlates.

The confusion between place, activity, and trips needs to be clarified to make the home a single place and not report travel within the home. The home round trip can be complex as stops proliferate, but can be simplified by separating home round trips from the rest, and HH from two trip pairs. The number of stops can be limited to reduce the proliferation of empty spreadsheet cells that bulk up file size and slow down computations.

The household transportation surveys use lists of purposes which are adequate for some purposes are not as useful for evaluation of neighborhood mobility. Household surveys and home round trip analyses should look at combining goods and services purposes that

Are frequent and routine, 10 I asked the CHTS analyst Evan Burton “Is there some way to analyze the data that would look at the data set in terms of home start and home end trips and trip chains that take place with six hours or less of travel time on the same day?” He replied: “In the processed data there is a flag in the trips and days tables to indicate if the trip began at home/work/or school. These are the last columns in the tables [that I’ve sent to you]. To create this I used the home/work/school locations identified in the full survey to compare the start and end of each trip against these points. If the start and end is within 0.05 decimal degrees of the point it is flagged as starting or ending at that location. “Also in the original study the places table will contain something similar. The original data available is the original version of the database, and the processed is a normalized version that allows for comparison across studies. They should both allow this.” Email and phone calls, May to December 2014.

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Are generally close to home location, Have short travel times, and Are frequently combined with other trips, particularly routine shopping and

services, often done in conjunction with a major activity like work, education, or frequent family obligation.Similarly, infrequent, longer trips with apparently different purposes may be functionally

similar for analyzing neighborhood performance. They could be grouped into categories by increasing travel time and decreasing frequency and aggregated to reach statistical significance. In some cases a single significant purpose does, in fact, have a wide spread of travel times.

Household surveys should try allocating serve passenger and vehicle per se trips to their real purposes, which would tend to make auto trips longer and walkable neighborhoods more competitive.

Education should be split between school for children and higher education for adults; they are very different kinds of trips.

Evaluation of neighborhood systemsWalk, bike, and transit cannot compete with the auto on speed, but they can compete on

travel times, with density and design bringing destinations closer together. A careful review of four major surveys for a long list of trip purposes reveals the purposes most important for evaluating neighborhood performance against survey norms. Quantification of travel time budgets allows measuring how well walkable neighborhoods perform, instead of simply assuming they do.

Especially important for where people choose to live are trips for work and work related (23 percent of total time; 23 minutes average trip time) and for education (9 percent of total time and 18 minutes trip time). Combined, they are 32 percent of total travel time. Walkable systems need transit to more distant work and education locations to have acceptable non-auto travel times.

The education trip broadly divides between school and higher education. Higher education, with adult trip makers, has longer, independent trips, for which travel time is important. For schools, however, children usually do not travel far and there are many serve passenger trips, and travel time alone is too superficial as a criterion. A fast trip to a bad school in a walkable neighborhood does not help.

Meals away from home and routine shopping and services have 27 percent of total travel time, and involve more people than workers and students. Meals away and routine shopping and services are more frequent and with shorter times than work and education, but are less important for choice of neighborhood because the relevant businesses respond to local market demand and locate close to housing. Meals away from home and routine shopping and services also lend themselves to home round trips, both as part of a work or education trip and as an errand trip. If the relevant businesses cluster close together, they can support efficient walking times for home round trips. Autos in suburbia can function with dispersed locations, while a walkable neighborhood has to concentrate these destinations for attractive walk distances.

A number of other purposes—special shopping, health, exercise, civic/religious, entertainment, socializing, special social--add up to 30 percent of total travel time, and seem likely to be met by some combination of local business, transit to a center, and carshare/rental.

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Carshare/rental is essential for walkability and as fast as an auto for non-routine trips. While the cost per trip for carshare/rental is higher than suburbia, there are even greater savings from not owning a car. These kinds of trips do not seem to affect the locational decision or time budgets for errands.

Most surprising is the importance of serve passenger trips and vehicle per se trips, totaling 15 percent of trips and averaging 14 minutes and 19 minutes respectively. Most of these trips seem due to automobile dependency, but serving child travelers would also be necessary in a walkable system. Nevertheless, a walkable system seems likely to outperform suburbia by having a small fraction of these kinds of trips.

Travel times can be quantified for evaluation of neighborhood systems, bringing a deeper analysis to a generally understood pattern for walkability: efficient home round trips based on locating transit for work trips and infrequent trips close to a concentration of local businesses for meals away, routine shopping and services, and other common needs.

8 ReferencesURL for data used in article:

https://www.dropbox.com/sh/0mkujqvpqaryad8/AABCheL6fx1X7HobQk4LrcIPa?dl=0 for a large folder of mobility data https://www.dropbox.com/sh/xgmc5sgr65nq6ya/AACskWSHtbmyFUusc9xqUgCZa?dl=0 for a folder used for this specific article

ATUS. 2012. U.S. Department of Labor. Table A-1 Time spent, ATUS Table 2 number, ATUS Table 2 percent, coding; lexiconwex2012. American Time Use Survey. http://www.bls.gov/tus/#tables.

BATS. 2000. Metropolitan Transportation Commission (MTC). Bay Area Transportation Survey 2000. MTC 2000RegTravCharReport.doc

CHTS. 2011. California Department of Transportation. California Household Travel Survey. http://www.dot.ca.gov/hq/tpp/offices/omsp/statewide_travel_analysis/chts.html. Also the Transportation Secure Data Center, National Renewable Energy Laboratory (NREL). http://www.nrel.gov/vehiclesandfuels/secure_transportation_data.html

Krizek, K. 2003. Neighborhood services, trip purpose, and tour-based travel. Transportation 30: 387–410, 2003.

Lewis, S. 2015. C:\Users\Sherman\Dropbox\Travel Time budgets\ Household Surveys and Travel Time Budgets.xlsx. https://www.dropbox.com/sh/xgmc5sgr65nq6ya/AACskWSHtbmyFUusc9xqUgCZa?dl=0

Litman, T. 2014. Executive Director, Victoria Transport Policy Institute. Email to Sherman Lewis, 7/7/2014

Mokhtarian, P and C. Chen. 2004. TTB or not TTB, that is the question: a review and analysis of the empirical literature on travel time (and money) budgets. Transportation Research Part A. http://escholarship.org/uc/item/3kr185ts

Mokhtarian, P. and I. Solomon. 2001. How derived is the demand for travel? Some conceptual and measurement considerations. Transportation Research Part A 35 (2001) 695-719.

NHTS. 2009. U.S. Department of Transportation, Federal Highway Administration. 2009 National Household Travel Survey. Includes NHTS Trip Chaining Dataset, Trip chaining tour09 78864 rows V cols w analysis.xlsx and DAYV2PUB NHTS original.xlsx.

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http://nhts.ornl.gov)Santos, A., N. McGuckin, H.Y. Nakamoto, D. Gray, and S. Liss. 2011. Summary of Travel Trends:

2009 National Household Travel Survey. U.S. Department of Transportation, Federal Highway Administration. http://trid.trb.org/view.aspx?id=1107370

9. AcknowledgementsShimon Israel, Associate Transportation Planner/Analyst, MTC, 510-817-5839

SIsrael@mtc.ca.gov.Evan Burton, NHTS, Evan.Burton@nrel.gov