Tuesday, June 27, 2006

The Yellow Caution Light

I was at the bank today and overheard a lady say she got a ticket at Coldwater and Coliseum while making a left turn from Coldwater onto coliseum. She said she saw an individual standing behind a light pole on the corner. She was in the intersection waiting for an opportunity to turn left and when it was clear, she turned. At the same time the light turned yellow. She said she made it through the intersection before it turned red. As she pulled straight flashing lights came on behind her. She was cited for a running a yellow light.

My wife also told me she saw on the news something about police issuing citations for those passing through on a yellow caution light. I would like to make a few observations:

  • A four-lane intersection is about 40 feet wide.
  • The pedestrian walkway sits back about 3 to 4 feet from the intersection.
  • The pedestrian walkway is about six feet wide.
  • The white strip painted on the road to indicate where your front end is to stop at is about four feet from the pedestrian walk way.
  • Total travel distance to clear both the intersection and pedestrian right of way is a minimum 65 feet. This now makes a standard four-lane intersection about 60 feet wide.
  • A car traveling at 30 mph is traveling at 44 ft/sec.
  • A 30 mph speed limit would require a minimum of 1.5 seconds to just clear the intersection and pedestrian right of way.
  • The average reaction time of an individual is 1/2 second. Though this is not the mean distribution point it would indicate roughly about half the population is faster and about half slower.
  • To ensure that 98% of the population's reaction time is fast enough to observe, analyze their speed, distance they have to stop and surrounding traffic would most like increase the reaction time to respond to a full second if not more.
  • In essence the yellow light duration for a standard 4 lane intersection would be a minimum of 2.5 seconds, but that only takes into account those who do not have time to stop. What about those who decide to stop? How much time do they need and what travel distance is needed to stop?
  • From what I can gather from looking for standards on yellow light duration, there are none, but if there are they are not readily accessible to me.
  • The Indiana BMV drivers manual has stopping distances for different speeds. Are these emergency stopping distances or are they stopping distances needed for coming to a non-emergency stop?
  • Clearly if you were to use the stopping distances in the manual and calculate the time it takes stop assuming the distance, initial velocity to be the speed limit and final velocity to be zero and add this to the 2.5 second time to get through the intersection, you will find you need about 5 seconds.
How many yellow lights last 5 seconds? The intersection with turn lanes make it even wider and longer. If traffic is traveling slower let us say 20 mph, it will take nearly another full second to get through.

The purpose of the yellow light is to indicate to on coming traffic approaching the intersection that the light is going to turn red. Its purpose is to keep people from jamming on their brakes, causing accidents. It is so that cars are less prone to be in the intersection when it turns red. It is to clear the intersection so that a controlled change in direction may take place. It is a safety feature that traffic engineers use to safe guard the public.

The Fort Wayne Police Department is wrong to be citing people for going through yellow lights. The police are manually taking this safety feature out of service. They are endangering the population by doing this. This in my opinion is criminal intent to do bodily harm.

I am going to do more research on this matter. I would like input from others as to how long they observe yellow lights and their locations.

Indiana Bureau of Motor Veihcials Driving Manual 2005 Edition states on page 30 and 31:
For Vehicles Proceeding Straight through Intersection:
  • A green signal means go. The driver has the right-of-way and may proceed through the intersection provided it is clear of other traffic and pedestrians.
  • A yellow signal means that the right-of-way is ending.
  • A red signal means stop. Traffic entering the intersection from another direction has the right of-way. The driver may not enter the intersection until the light turns green and the intersection is clear of other traffic.
For Vehicles Turning at the Intersection:
  • A green arrow displayed in conjunction with a red or green signal means the driver has the right-of-way to make the turn so long as the intersection is clear. Oncoming traffic must stop.
  • A yellow arrow displayed in conjunction with a red or green signal means that the right-of way to turn is ending.
  • A green signal alone means that the driver may make a turn so long as the intersection is clear and the driver yields the right-of-way to all oncoming traffic. When making a left turn on green, only one vehicle is allowed to move into the intersection to complete the turn when the way is clear. Always make sure that the oncoming vehicles are going to stop.
  • A yellow signal alone means that the period to turn is ending. As stated above, if you are in the middle of the intersection, complete your turn once the oncoming traffic has stopped.
  • A red signal alone means stop. Drivers lawfully within the intersection shall complete the turn. Traffic entering the intersection from another direction has the right-of-way when conflicting traffic is no longer present. The driver may not enter the intersection until the light turns green and the intersection is clear of other traffic.

NOTE: Traffic facing a steady red signal alone shall stop at a clearly marked stop line.


I just found this:
IC 9-21-3-1
Standards and specifications
Sec. 1. Each traffic control signal on a street or highway within Indiana must conform with the standards, specifications, and warrants set forth in the Indiana Manual on Uniform Traffic Control Devices for Streets and Highways.
As added by P.L.2-1991, SEC.9.

Though I did not find it on-line, the Allen County Public Library has a copy:

Indiana manual on uniform traffic control devices for streets and highways : signs, markings, and traffic signals
Indiana. Dept. of Highways.
Publisher: Indiana Dept. of Highways,
Pub date: 1988-
Pages: 1 v. (loose-leaf) :
Owned By Agencies Below
MAIN # of Copies Material Format Location
343.77209 IN2 1 Book Bus & Tech Reference

I will be making a stop and will let you know what I learn.


At 3:33 PM, Anonymous Bob G. said...

I agree with your assessment of the entire traffic light situation and your concerns.
I have NEVER seen a FIVE second yellow light.

I suppose Sgt. Bonar has to pay some bills with all the O/T he's raking in "uptown" (I believe he made more than the CHIEF and the mayor).

And here WE are...on the SOUTH side...with ALL the vehicles I see with blown out lights, non-functioning mufflers, RED light runners, speeding, illegal u-turns and boomcar noise violations. Gee...we actually NEED a man like Sgt/ Bonar HERE instead of Coldwater & Coliseum....do we not?

I ask you...where IS the justice, becasue I'm just not seein' it?


At 1:48 PM, Blogger Scam Stoppers said...

I got the same ticket yesterday (tuesday) I had the same ideas on the subject. I am going to court Aug. 28th and plea NOT GUILTY on these same grounds and the Statute I.C 9-21-3-7 wording which states that " a yellow light means that the color will soon turn red" Nothing about stoping. All drivers know that a panic stop on yellow at an intercetion would cause a rear end collision!

At 8:58 AM, Blogger William Larsen said...

Scam Stoppers,
To help you with your case, I would suggest you take a digital photo of the intersection in question. I would also time the yellow light sequence (video would be good to document the actual time – be sure to have date-time-seconds displayed). Knowing the speed limit will help determine the time it takes to stop.

For example assuming linear acceleration and deceleration we might approximate the distance needed to stop. If it takes 8 seconds to go from zero to 60 mph or 88 feet per second, then we know the acceleration to be 88 feet per second divided by 8 seconds would result in 11 ft/sec^2. We then calculate the distance traveled from a dead stop to 60 mph to be Displacement = (initial velocity) * (time) + ½ * (acceleration) * (time)^2.

Initial velocity is zero leaving ½ * (11 ft/sec^2) * (8 sec)^2

It would take 352 feet of travel to reach 60 mph. We could then say we certainly do not want to stop at the same rate we could accelerate (fast acceleration is reckless). So we reverse the calculation. At 30 mph it would take 5.3 seconds to come to a complete stop based on a deceleration of 11 ft/sec^2. You would have to begin stopping 156 feet prior to the white stop line of the intersection to stop in time and it would take 5.3 seconds to do so. This would then require some amount of reaction time as well, further increasing the time and distance to stop SAFELY.

You might also try the following. A speeding ticket can generally be thrown out if the radar has not been calibrated or if the officer cannot produce a calibration record. Like all things that are electronic, they periodically need calibration and their functions measured and validated. How often do you think traffic light timing is done?


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