Winnipeg Yellow Adequacy for Various Speeds

7/28/2019 Winnipeg Yellow Adequacy for Various Speeds

1/3

Are Winnipeg's Yellow Lights Adequate?

All yellow lights in Winnipeg are 4.0 seconds and are timed while assuming that the law

regarding yellow timing is permissive. A permissive law means that vehicles are allowed

to enter the intersection until to the end of the yellow duration and possibly clear duringthe red. Under this type of law, the yellow must be long enough only for any vehicle thatis too close to the intersection to stop when the yellow is first displayed to enter the

intersection before the red. The stopping distance is determined by three variables, the

initial speed, the rate of deceleration and the perception/reaction time. According to

various Institute of Transportation Engineers (ITE) documents, the rate of deceleration is-10 ft/s

2and the perception/reaction time is 1 second. Using this information, it can be

determined if Winnipeg's yellows are adequate for each speed zone.

80 km/h Intersections

A vehicle travelling 80 km/h is moving at 73 ft/s. With a deceleration rate of -10 ft/ s2

, itwill take 7.3 seconds for that vehicle to stop. The average rate of speed during that time

is going to be 36.5 ft/s. While stopping, the vehicle will travel 267 ft (36.5 ft/s x 7.3 s)and when that is added to the 73 ft travelled during the perception reaction time, it is

found that the stopping distance at 80 km/h is 339 ft. With a 4.0 second yellow, vehicles

are only able to travel 292 ft (73 ft/s x 4.0 sec) during the duration of the 4.0 second

yellow. This creates a 47 ft area where a vehicle can neither stop before the intersectionor enter before the red and that known as the dilemma zone.


A vehicle travelling 70 km/h is moving at 64 ft/s and will take 6.4 seconds to stop.During the stopping and perception reaction time, the vehicle will travel 267 ft. With a

4.0 second yellow, vehicles are only able to travel 255 ft during the duration of the

yellow creating a 12 ft dilemma zone. The dilemma zone still exists at 70 km/h

intersections but is not as large as in 80 km/h intersections.


2/3


A vehicle travelling 60 km/h is moving at 55 ft/s and will take 5.5 seconds to stop.During the stopping and perception reaction time, the vehicle will travel 204 ft. With a

4.0 second yellow, vehicles are able to travel 219 ft during the duration of the yellow.

When the stopping distance is less than the distance travelled during the yellow duration,the opposite of a dilemma zone is created which is called an option zone. The option

zone is the area where a vehicle can both stop or go when the light turns yellow. At 60

km/h intersections, the option zone is 15 ft long.


A vehicle travelling 50 km/h is moving at 46 ft/s and will take 4.6 seconds to stop.

During the stopping and perception reaction time, the vehicle will travel 149 ft. With a4.0 second yellow, vehicles are able to travel 182 ft during the duration of the yellow

creating a 23 ft option zone. Due to the lower speed, the option zone is larger than it is

for a 60 km/h intersection.


3/3

Conclusions

Winnipeg is the only major city in western Canada that doesn't increase the duration of

the yellow signal for high speed intersections. This creates what is known as a dilemma

zone for many drivers in 70 and 80 km/h zones who get caught into a situation where

they can't stop or go. To adapt, Winnipeg is forcing drivers caught in this zone to breakharder than the values accepted by engineering standards. Drivers who are unable to do

this will get caught by the red light cameras. This is why cameras in 80 km/h zones issue

600% more tickets than those in lower speed zones.

The dilemma zones represented in this document are the absolute minimums. They can

be considered even larger by the standards used in some other jurisdictions. The

perception reaction time used for these calculations was 1.0 seconds. Some jurisdictionscalculate using a 1.5 second and sometimes up to a 1.8 second perception/reaction time

which increases the stopping distance. In addition, many jurisdictions calculate their

yellows using the travelling (85th percentile) speed instead of posted limit. When this is

done, the yellow is normally calculated using the speed limit plus 7 mph. If consideringhigher travelling speeds or longer perception/reaction times, the yellows in Winnipeg are

even more inadequate.

The problem with these calculations is that they rely on drivers being allowed to legally

enter the intersection on yellow and clear the intersection on the red under a permissive

yellow. In reality, the Manitoba Highway traffic act states that:

Yellow traffic control light or arrow at intersection

88(5) When a yellow or amber traffic control light or arrow is being shown at an intersection by atraffic control signal following or accompanying a green traffic control light,

(a) the driver of a vehicle at or approaching the intersection and facing the light or arrow shall notenter the intersection, unless he can leave it before a red traffic control light or such other signalas next follows, begins to be shown; and

This law means that Manitoba has what is called a restrictive yellow and is the onlyprovince to have that type of law. Under this law, yellow lights not only have to be long

enough for traffic that is caught within stopping distance of stop line to enter the

intersection before the red, but must also must be able to cross the intersection. Yellowlights in Winnipeg need to be timed to remove the dilemma zone in higher speeds and as

long as the HTA remains as it is, must be even longer to allow traffic to clear the

intersection before the red.
http://web2.gov.mb.ca/laws/statutes/ccsm/h060f.php#88(5)http://web2.gov.mb.ca/laws/statutes/ccsm/h060f.php#88(5)http://web2.gov.mb.ca/laws/statutes/ccsm/h060f.php#88(5)

Winnipeg Yellow Adequacy for Various Speeds

Documents

Transcript of Winnipeg Yellow Adequacy for Various Speeds