Can Longer Yellow Lights Make Intersections Safer?

Photo by AlexandreNunes via Shutterstock

Some groups think so and are advocating for them, as the era of red-light cameras in Los Angeles comes to a close.

Red-light cameras were hailed as a way to make intersections safer, but the program ended up being a sieve for city dollars and some groups complained that the cameras actually increased certain kinds of collisions caused by people braking to avoid a ticket.

One group Safer Streets L.A. is pushing for longer yellow lights in Los Angeles, so that drivers have time to clear the intersection:

If the yellow signal phase is too short, a “dilemma zone” is created. Motorists who are unfortunate enough to be within this section of the roadway when the yellow signal illuminates may neither be able to stop safely nor legally enter the intersection before the onset of the red phase. Dilemma zones virtually assure that some percentage of drivers will be forced to brake suddenly or violate the red, thereby creating the potential for rear end collisions or vehicle conflicts within the intersection.

But city transportation officials disagree, saying that extending the time at some of the city's most dangerous intersections could actually make matters worse.

As city officials voted to completely kill the red-light camera program, Pauline Chan, a senior engineer for LADOT, fielded questions about yellow lights from the city council. She told them she is against lengthening yellow lights. Instead she suggested looking at collision data to figure out how to reduce wrecks.

"I believe that looking at four intersections ... over a very short period of time, because of monetary restrictions, would have probably very limited use and probably would not help us evaluate traffic safety impacts of extending the signal timing," Chan said.

Councilmen Bernard Parks and Mitchell Englander wanted to keep cameras up at four intersections to test whether extending the length of yellow lights would lead to fewer red-light violations, but the council ended up voting to take the cameras down entirely.

The city's transportation committee says it will continue to look into the yellow light issue and revisit it later.

Contact the author of this article or email tips@laist.com with further questions, comments or tips.

By Emma G. Gallegos in News on September 15, 2011 11:10 AM

Comments [rss]

William Cervantes

i think a good idea for yellow lights are to put a count down number next to the yellow light (or maybe in the center of the light). once the yellow light turns on, a number counts down from 5 to zero. that would give motorist a good idea of how much time they have left to cross the intersection or make a left turn and reduce rear end collisions and other accidents.

hN9S9

2 per red...thats the rule!

DiegoHenry

While we are distracted by LA's fight over longer yellow lights, yellow lights are about to be shortened, statewide. By the stroke of a pen.

A bill in Sacramento will allow cities to reduce posted
speeds by 5 mph, even on streets with a great safety record. That will allow
them to shorten yellows, which will increase red light cam ticketing by at
least 50%. (Four of the sponsoring cities have red light cams.) Worse, the
shortening will increase severe accidents by 30 to 40%. (Source:
"Development of Guidelines for Treating Red-Light Running," Texas
Transp. Inst. pg 2-20.)

AB 529 is now (right now!) on Gov. Brown's desk for signature - or veto.
Phone him at 916 445-2841, or email him via the form at gov.ca.gov. Ask him to veto. Also phone your union or professional assn. As soon as possible.

To the supporters of 529: Remember that 529 will increase
severe accidents, a lot, just for $$.

Pete Davis

Here's an idea, if we're talking about adding lights and making intersections safer; how about a more widespread use of dedicated left turn lights? Most accidents I've seen in LA are from cars attempting to turn left as the other guy tries to rush through the red light.

Jay Beeber

A protected left (red arrow) is always the safest choice for the left turn lane. Unfortunately, you have to strike a balance because it also causes delays if there are more cars waiting to turn left than can be accommodated during the green arrow phase.

Doran

I think a wider use count-down timers would be more helpful than longer yellow lights.

Jay Beeber

The countdown timers are help, but unfortunately they are not standardized to always count down to zero as the light turns yellow.

Defunder Funtime

No. A longer delay between once the initial light turns red and the other light turns green would help though.

Paul

That's exactly what I was going to say. Longer yellow lights would just mean more people think they have more time to run it - making it extremely dangerous for people who are making left hand turns.

However, if all both sides were red for just an extra second or two before the other side turned green - yellow light runners would have enough time to clear before cross traffic goes...at least until people figure out the timing and then we're back to square one.

Jay Beeber

There is absolutely no data to suggest that longer yellows make people think they have more time to run the light. The longer yellow eliminates the dilemma zone, which is created by the difference between the actual speed of traffic approaching the intersection and the posted speed limit (which is what the time is based on now). This gives drivers more time to stop and they are more likely to do so. In every place where the yellow light was lengthened, violations went down significantly and stayed down, even months after the timing change. Even John Fisher, Asst. Mgr of the DOT admits there are no studies to show that drivers adjust to longer yellow times and that the belief is just "the conventional wisdom". Of course you also need a long enough all-red phase as well to account for those that cross into the intersection just before the light turns red.

Paul

Are you kidding me? Have you seen people drive? Do you notice your surrounding?

I've seen people from far away distances - way before the crosswalk - not slow down and/or speed up even though they are far away and the light is yellow. They're supposed to stop, but they don't.

Most drivers are a-holes - and extending the yellows well just make them aware that they have plenty of MORE time to cross from half a block away. Sit at a corner one day on any intersection and you'll see what I'm talking about.

Jay Beeber

The problem with this belief is that when the yellow light time is extended, sometimes by as little as .3 seconds, violations drop significantly and stay down over time. In Loma Linda, they had a light timed .3 seconds under the minimum time. There were about 200 violations per month. They increased the time by .3 seconds and the
violations went down by 75% to about 50 per month and stayed at that rate for a couple of years. About 9 months before they ended the camera program they increased the yellow by another 1 second and violations
dropped another 90% to about 5 per month. That means that the violations that occurred prior to the time change wouldn't have occurred if the yellow was simply a little longer.

Just because there are some bad drivers doesn't mean that there aren't many others who will be less likely to violate the red when presented with a longer yellow light. All the data shows this to be true, your personal perception notwithstanding. And most drivers aren't a-holes. The vast majority of motorists drive in a reasonable and prudent manner. It's the few bad ones that you notice, hence giving you the impression that "most" drivers are bad.

Marcial

I agree with the last two posters. I also think that all intersections should have the pedestrian timers. It helps when you are unsure of whether to cross the intersection or not.