Judith White wants to know why Wichita's stoplights can't be coordinated
Have you ever been stopped at a red light downtown, but as you wait, no other cars pass in the other direction?
Or driven down Rock Road and had to stop at every single light?
Does it feel like you’ve been waiting at stoplights a little more lately?
Judith White, a retired educator in Wichita, has been wondering this for awhile. She drives once or a twice a day for 15 to 20 minutes: to the hairdresser, to physical therapy and to the supermarket. “And it just gets frustrating at the number of times I have to stop.”
With all the ways that computers have changed life, White wondered, why can’t computers be used to coordinate Wichita’s stoplights? Not only would it save time, but it would be better for the environment and save gas money, she said. White submitted her question to Curious Wichita, the Eagle’s series on reader questions.
It turns out that Paul Gunzelman, the assistant city engineer – the man most responsible for Wichita’s traffic lights – has been wondering the same thing. And he believes a solution is coming.
The city initiated two studies that could lead to decreased waiting time at stoplights. One of the biggest problem areas is downtown, Gunzelman said, and there’s several reasons.
Most downtown stoplights can’t detect traffic. In the rest of the city, sensors in the road or cameras above it, can tell the stoplights if there is no traffic. That way, late at night, if a driver is the only car stopped, the light knows to change.
Downtown, drivers just have to sit and wait. Even if no traffic is coming down St. Francis, drivers at the intersection with Central still have to sit there and wait.
Another problem: There are hardly any crosswalk buttons for walkers. And downtown is supposed to be one of the most walkable parts of the city. Not only does this mean pedestrians have to wait longer to be able to cross, but they can throw off the whole stoplight cycle. Without pedestrians, more cars could keep driving through.
The type of stoplight used downtown, referred to as a model “170,” is more than 20 years old, according to Gunzelman. The timing gets thrown in the older stoplights. Twice a day the city remotely resets the downtown stoplights before rush hour, so that they fall back into alignment. The newer traffic lights, the “2070s,” used throughout the rest of the city don’t have this problem.
Most of the stoplights have outmoded equipment for sharing information. Right now many of them communicate by old-fashioned phone lines, like a dial-up modem, rather than fiber optic cables, like high-speed internet. And many of these communication systems are not currently functional. This limits the city’s ability to coordinate a response when, for example, there is an accident.
One of the biggest reasons for the new study is that traffic patterns have changed. Some one-way streets became two-way when Intrust Bank Arena opened, and the stoplight patterns haven’t changed. New businesses have emerged along Douglas, and stoplight patterns haven’t changed.
Each of these little problems compound and can make the average person’s wait time just a little longer.
The last big study to make Wichita’s stoplights smarter was funded in 1998, Gunzelman said, and the work was done in the early 2000s. It was time to look again at how to make them better, he said.
Gunzelman thinks the city can save Wichita drivers time. The city is counting cars on roads and taking inventory of its equipment. In addition to downtown, the study is focused on two other areas – Rock Road and Central. Recommendations are expected by the end of the year.
How it works
Each intersection, when looked at from an engineer’s perspective like Gunzelman’s, is a kind of small ballet production, with many dancers that all have to be choreographed carefully, so they don’t slow down the whole production or crash into each other.
When a light turns green it has to stay green for about a minute in most places in the city and that can’t be reduced. That’s determined by how fast people walk. Engineers don’t want elderly or disabled walkers to have to dodge traffic because of their slow gait.
But engineers can increase the amount of time lights stay green. By allowing lights on busier streets to stay green longer, they can carry cars through more swiftly. Not every street is considered equal.
But the engineer’s job is not just to figure how long to hold the green light in each direction. Engineers want each green light to be coordinated with the other green lights down the road.
They don’t want them to turn green at the same time—that would encourage drivers to speed through all the lights before they turned red again.
Instead, engineers try to make the lights “cascade,” one after the other, like a waterfall. So that a driver whose light just turned green will not have to slow down before the next one turns green. When everything is working right, a driver shouldn’t have to stop at more than one downtown stoplight in Wichita.
But if you are a driver, sitting at a stoplight late at night with no other cars coming, that beautiful cascade of lights in front of you is wasting your time. It makes no sense to have a car wait at a stoplight by itself.
If the light can turn green for a woman who wants to head north, it could ruin the whole cascade of green lights for a man heading east. Now the man, who was only two blocks away, is annoyed that he has to stop. A good traffic light for one driver can be a bad traffic light for another.
So the city has to make choices about which streets and which intersections to give priority to and at what times of day.
One-way streets are simpler because they don’t have to take into account left turns, which can make traffic in all directions stop. The traffic dance is further complicated during the frenetic rush hour when the streets fill up, often in one direction more than the other. The city has different stoplight times between 7 a.m. and 9 a.m. and between 4 p.m. and 6 p.m. than it does during the rest of the day.
After the stoplights have been improved, the city could improve traffic flow after a highway accident. As drivers pull off or take alternate routes, stoplights can be changed to allow for that unexpected traffic on cross streets to drive through more quickly.
During a Wichita State Shockers game, stoplights could be changed to let people get home more quickly.
But Gunzelman can’t say how soon this will happen. Right now the budget for traffic lights is limited to $500,000 per year. If the budget isn’t increased, the city will have to make choices about what to prioritize and it could take years to install all the new equipment.
Los Angeles recently finished spending $400 million over 30 years to make its traffic lights smarter. The result: the city reduced the time it takes to travel a distance of five miles from 20 minutes to 17 minutes.
When that savings is multiplied by millions of people over many years, that’s a lot of savings on time, gas and pollution.
But traffic in Los Angeles is terrible and much more spread out.
And new traffic signals can cost thousands of dollars to install and thousands more to maintain. So it’s unclear how much Wichitans will be willing to spend to save a few minutes a day.
“It’s what you are used to,” Gunzelman said. “I think most people around here, if they can’t get through one light but it takes two, they think we have traffic issues. People who travel realize how much traffic other cities have, and how much worse it could be.”