Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system...
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Transcript of Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system...
![Page 1: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/1.jpg)
Vehicle Flow
![Page 2: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/2.jpg)
Homework
• Ch 5 # 1, 2, 4, 7, 9
![Page 3: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/3.jpg)
Vehicle Flow
• How do vehicles operate in the system– capacity– speed – headway– density
![Page 4: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/4.jpg)
Time Space Diagrams
• Show vehicle location vs. Time– one way or two way– any type of transportation system– used to find
• siding placement• progression• minimum headways• Throughput
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City B
City A
10 20 30 40
A-> B = 500miTrain A -> B loaded speed = 30mphTrain B -> A empty speed 50 mph
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Vehicle Following
• Spacing needed for stopping
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Deceleration
• 3 types of deceleration– Normal dn = 8fps^2– Emergency de = 24fps^2– Instantaneous
• Initial spacing– S = v +v^2/2df –v^2/2dl +NL +x0
• Safest spacing when lead vehicle decelerates instantaneously and following vehicle brakes at normal deceleration
![Page 8: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/8.jpg)
Example
• What is the safe initial spacing between two vehicles traveling 40 mph if the lead vehicle uses an emergency deceleration of 24 fps^2 and the following vehicle normally decelerates at 8 fps^2? PR time = 1.5 sec, vehicle length = 20 feet, x0 = 4 feet
![Page 9: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/9.jpg)
Flow Concepts
• 4 variables– volume– speed– density– headway
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Volume
• # of vehicles passing a given point in a given unit time
• q = n/T
• cars per hour
• does not tell you anything about speed or density
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Speed
• 2 types– Space Mean Speed
• distance divided by time
• useful in determining vehicle flow characteristics
– Time Mean Speed• Spot speeds
• Radar gun
• not useful except for tickets
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Example
• Si = 2 miles, i = 1 - 4• v1 = 42 mph, v2 = 39 mph, v3 = 47 mph,
v4 = 50 mph– Average V = 44.5 mph
• m1 = 3.1 min, m2 = 2.8 min, m3 = 3.3 min, m4 = 3.0 min– Average = 39.5 mph
• What is the difference, is it significant?
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Density
• Concentration– vehicles per unit length– cars/mile
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Headway
• Time or distance between two vehicles– h = 1/q gives the time headway– h = 1/k gives distance headway– which is more useful?
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Relationships
• q=uk– basic relationship
• Important points– jam density– jam speed– max volume
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Relationships
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Relationships
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Relationships
![Page 19: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/19.jpg)
Relationships
• Shape of curves– what do they tell us?
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Example
• The u-k relationship is – u + 2.6 = 0.001(k – 240)^2– Find umax, jam density, and max capacity
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Shock waves
• Happens when traffic is forced to change speed either slowing down or speeding up
– shockwave
• Can move either forward or backward– usw = (qb – qa)/(kb – ka)
– a, b are 2 points of interest• If shockwave is + => heading in direction of flow
• If shockwave is 0 => stationary
• If shockwave is - => moving against flow
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Example
• A line of traffic, moving at 30 mph and a concentration of 50 veh/mi is stopped for 30 sec at a red light. Calculate the velocity and direction of the stopping wave, the length of the line of cars stopped during the 30 sec of red, and the number of cars stopped during the 30 sec of red. Assume a jam capacity of 250 veh/mi
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Control of Vehicle Flows
• Control vehicles– minimize accidents– maximize effectiveness
– transit
– airports
– roadways
• Channelization most common control
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Control of Vehicle Flows
• Speed limits
• Control on Links– signage– lane width– number of lanes– headway rules
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Headway Rules
• RR - uses block system
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Headway Rules
• Aircraft– Airports
• 1 aircraft on runway at any time
• separation distances – 2.5 miles between aircraft
– 10 miles horizontal / 2000 ft vertical in air
– Control based on aircraft location
• Ground control for aircraft not on runway
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Capacity
• Capacity based on mode
• # of vehicles per hour
• # of passengers per hour
• arrivals, departures per hour
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Highways
• Capacity varies by road type– Freeways
• no controls,
– Intersections• traffic control
– 2 lane & 4 lane roads• lead vehicle
• All use Level of Service
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Determining Capacity
• Based on Roadway geometrics and traffic conditions
• For Freeways– can determine ideal conditions and from that a
maximum capacity
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Peak Hour Factor
• Measures demand peaking
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Level of Service
• LOS can be based on– delay per vehicle– speed– service flow
• 6 LOS A - F– A is best– F is worst
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Freeway Capacity
• LOS based on – density– speed– v/c
• For an LOS can find Maximum Service Flow (MSF)
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MSF
• MSF = qmax*(v/c) - ideal conditions
• SF = q = qmax*N*fw*FHV
• Table 4.3.3 for heavy vehicle factors
• Table 4.3.2 for width factors
![Page 34: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/34.jpg)
Capacity Restrictions
• Non recurring
• Recurring
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Example
• Ch 4 # 14
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Pedestrians
• LOS based on– speed– flow rate– v/c ratio
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Bike LOS
• Based on amount of hindrance
![Page 38: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/38.jpg)
Airports
• Capacity depends on landside and airside
• LOS is based on delay and total time
• Why are airports becoming shopping malls?
![Page 39: Vehicle Flow. Homework Ch 5 # 1, 2, 4, 7, 9 Vehicle Flow How do vehicles operate in the system –capacity –speed –headway –density.](https://reader035.fdocuments.us/reader035/viewer/2022062515/56649d1f5503460f949f2550/html5/thumbnails/39.jpg)
Rail
• Mass transit– LOS based on pass/seat, space/ pass,
• both peak and off peak
• AMTRAK– LOS based on wait time, comfort, pass/seat