Does anyone know the yellow light formula?

Question

I just got a ticket for running a red light. At least that's what the cop said, I definetly entered yellow, but he probally saw me in the intersection as it was red. I timed the light, it's 3 seconds from yellow to red.

It's a left turn, 50mph zone, big intersection, 3 lanes,3 seconds seems short. So do you have any links that will point me in the right direction or a formla for it?

Thanks in advance.

I don't think you understand.

I'm going to court to fight it, im going to tell them I didn't have enough time to stop (because I didn't). I need to know the formula for determening how long a yellow light should stay yellow, because I feel that it's too low and cops are taking advantage of it being a fast yellow.

Thanks for the replies though!

Ok thank you two guys for being *****, sounds like someone was watching law and order last night.

Let me explain this to you simply, so you'll have a chance at understanding it.

The law does state you need to stop when you see a yellow light, EXCEPT if it's unsafe to do so. If you think going 30mph in a 50mph zone is speeding, then congrats, I always wanted to ride a tiny schoolbus too. I WASNT speeding, I HAD enough time to make the turn, if I did stop, it'd have been to a screeching hault.

The light is 3 seconds, it takes 3 seconds alone to make the turn. Here's a chart:

Light turns yellow (3 seconds to go) im 1 second away from entering the turn

(2 seconds to go till red) im entering the turn

(1 second to go till red) im in the turn 1 second

(REDLIGHT) im in the turn 2 seconds now

(REDLIGHT) im exiting the turn

Cop saw the latter, didnt see I didnt have enough time to stop, im sure that's why he was sitting there, to catch people at a short yellow

Answer 1

Y = t + V/(2a+2Ag)
Y= Yellow clearance interval in seconds
t= reaction time (use 1 second)
V= 85%percentile approach speed in ft/sec/sec [can use speed limit]
a= deceleration rate of a vehicle(use 10 ft/sec/sec)
A= Acceleration due to gravity (32.2 ft/sec/sec)
g= percent grade in decimal form(+for upgrade,- for downgrade) this is
unknown.
*Calculate the yellow clearance interval to the nearest 0.1 second




okay example or possiable answer

However, mathematical evidence will bear out whether this light
deserves a longer interval.

We need to make some observations about the way the formula operates.

Increasing V will increase the light interval.
Driving downhill (negative grade) towards a light will increase the
light interval and driving uphill towards it (positive grade) will
decrease the light interval.

According to the conditions you set forth, we have

Y = 1 + 50/(20+64.4g) for 50mph scenario
or
Y = 1 + 45/(20+64.4g) for 45mph scenario.

So the timing of the light depends entirely on the grade of the road,
if all the other variables are held constant.

These formulas are found by simply plugging in V=45, a=10, A=32.2.
Values for specific g can be calculated by plugging in the g in
question. A 3% grade would be entered as g=.03. I did multiple entries
(in the table below) by using the "table" function of a TI-89 graphing
calculator, but in principle any calculator or even long
multiplication can give you the results you need for a particular
value of g. Mathematically speaking the most important factor is
"order of operations": first the operations that occur in parentheses
should occur, then multiplication and division, then addition and
subtraction. So in this case, we tackle the parentheses first: 64.4
must be multiplied by g, then the result should then be added to 20.
Now this result can be used to divide 45. Finally, 1 should be added
to this number to get a value for Y.

Since we don't know the grade of the road, and since at this time I
cannot find a road manual that clearly indicates the maximum grade of
a road approaching an intersection, I will list all values of Y for
grades from -10% to 10%, which I know to be considered quite steep
(Trucks often get warning signs around 5% grade). I will go by
half-percent increases. So the chart at the bottom of my answer lists
the value of Y for both scenarios for all grades from -0.1 until both
scenarios have yellow light times less than 2.8. I will increase by
0.005 increments.

To spare you from having to read through a chart unnecessarily, let me
summarize the findings first: If the grade is less than 7% uphill,
your yellow light time is greater than 2.8s in the 45mph scenario. In
the 50 mph scenario, if your grade is less than 11% uphill, your
yellow light time is longer than 2.8 seconds. Unless an intersection
is at the crest of a very steep hill, then at least one direction
coming into the intersection will probably have a grade less than 7%.
Remember that if a road is climbing a hill, and it has an intersection
on it, one direction of the intersection has a positive grade and the
other direction has a negative grade. Unless the intersection has a
fancy light sequence, both directions of the road will have the same
green light, and so both will be subject to the same yellow light
timing. Presumably, the longer light timing (the timing for the
fellows headed downhill) should be used.



Appendix: Chart of yellow light intervals based on grade.

Remember, negative grade indicates a car approaching the light is
traveling downhill. All values for Y are rounded to the nearest .1
second. In the interest of space, I will not continue the chart after
it enters the realm where the light's timing should be greater than
2.8 seconds according to the formula.

Please excuse the length of this chart, but without knowing the grade
of the road this seems to me the best way to convey the necessary
information.

Grade 45 mph scenario 50 mph scenario
-0.1 4.3 4.7
-0.095 4.2 4.6
-0.09 4.2 4.5
-0.085 4.1 4.4
-0.08 4.0 4.4
-0.075 4.0 4.3
-0.07 3.9 4.2
-0.065 3.8 4.2
-0.06 3.8 4.1
-0.055 3.7 4.0
-0.05 3.7 4.0
-0.045 3.6 3.9
-0.04 3.6 3.9
-0.035 3.5 3.8
-0.03 3.5 3.8
-0.025 3.4 3.7
-0.02 3.4 3.7
-0.015 3.4 3.6
-0.01 3.3 3.6
-0.005 3.3 3.5
0.0 3.3 3.5
0.005 3.2 3.5
0.01 3.2 3.4
0.015 3.1 3.4
0.02 3.1 3.3
0.025 3.1 3.3
0.03 3.1 3.3
0.035 3.0 3.2
0.04 3.0 3.2
0.045 3.0 3.2
0.05 2.9 3.2
0.055 2.9 3.1
0.06 2.9 3.1
0.065 2.9 3.1
0.07 2.8 3.0
0.075 3.0
0.08 3.0
0.085 3.0
0.09 2.9
0.095 2.9
0.1 2.9
0.105 2.9
0.11 2.8

i hope this helps answer your question

Answer 2

Reguardless of the calculations or what you are going to tell the judge, you're still going to have to pay the fine. Your best bet is to get a lawyer and plead to a non moving violation. Here's why:

By law, amber lights mean that you must clear the intersection. If you enter the intersection when the light is yellow, technically, in every state of the union, you are running the red light. No ifs, ands, or buts. A judge isn't going to see it any other way either.

If you try to fight the ticket, and lose, and you will lose, you'll have to pay that fine and py the higher insurance for years to come. If you get a lawyer and plead to a non moving violation, you are still out some money, but your insurance rates won't increase. Creeping into an intersection waiting to make a turn isn't really legal either, but folks do it.

Your call though. Keep in mind, traffic laws are to keep you safe, but traffice enforcement is all about making money for the local authorities, and eventually the insurance companies.

but it's your money.

Answer 3

The yellow is for clearing the intersection, not for entering. If it was red while you were in the intersection, you ran the light. The yellow does not have to be long enough to let anybody enter and exit the intersection, only to allow a car that is already in the intersection exit.This is elementary driving procedure my friend. They will say in court that, if you couldn't stop you were driving too fast, and, driving too fast, you should have had plenty of time to go through. So you are either being convicted of speeding, or of running the light, take your pick.

Answer 4

I know about "stale green". Here's yer best bet. Go to court, tell the judge that by the time the light was Yellow, it was too late to stop, considering your speed. Might get lucky depending on your driving record.

Good luck!!

Sandy

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Answer 5

Go to court talk to the judge. You may be able to get out of the ticket