Skip to Content

This coverage is made possible by grants from the Central Corridor Funders Collaborative and The McKnight Foundation.

Minneapolis re-timing traffic lights so it’s go go go, but is that a good idea?

Minneapolis re-timing traffic lights so it’s go go go, but is that a good idea?
MinnPost file photo by John Noltner
New signal timing is in place downtown; changes in the rest of the city will be complete by next summer.

It’s every driver’s dream: You’re on a busy city street and as you approach each intersection, the traffic signal changes to green.

Instead of stop and go, it’s go go go.

Minneapolis is in the midst of an upgrade for its traffic-control system that includes a new computerized system that can re-time traffic signals to make traffic flow more efficiently.

New signal timing is in place downtown; changes in the rest of the city will be complete by next summer. The $11.2 million project is funded by a federal grant and state, county and city money.

City officials say traffic flow downtown could improve by 10 percent. The system also allows the city’s Traffic Management Center to analyze traffic patterns and activate and turn off left-turn arrows.

The idea behind the synchronization of traffic signals is simple: Traffic congestion costs time and money and increases emissions that contribute to air pollution. So nudging vehicles to move along with fewer stops and starts is a positive step.

Counterintuitive view

But some traffic experts have a counterintuitive view. Improving traffic flow, they say, encourages people to drive more.

“Any time you make it easier or faster or less congested on a road, the more people will drive,” says Dom Nozzi, a transportation consultant based in Boulder, Colo., who blogs at nozziwalkablestreets.com.

“When we introduce changes that make it less inconvenient or less congested, we induce new car trips that would otherwise not have happened,” he says.

That’s not the prevailing attitude among traffic engineers in most U.S. cities.

Earlier this year, Los Angeles completed a $400 million project that included synchronization of all of its 4,500 traffic signals. The city says a five-mile trip that took an average of 20 minutes without signal synchronization now takes 17.2 minutes. The average speed on city streets has climbed from 15 mph to 17.3 mph.

The U.S. Department of Transportation says travel times declined by as much as 34 percent after Syracuse, N.Y., optimized signal timing at 145 intersections.

Sitting in traffic costs time and money. A report released in February by the Texas A&M Transportation Institute found that we squandered an average of $818 each in 2011 while tied up in traffic.

The report said the total cost of wasted time and fuel to Americans was $121 billion — up $1 billion from 2010. It also concluded that clogged roads resulted in the release of 56 billion pounds of additional carbon dioxide into the atmosphere.

In the Twin Cities, the study found, congestion cost each commuter $695, 45th among metro areas.

Ryan Richter, an urban planner in Chicago who specializes in the relationship between land use and transportation, says most communities pursue traffic-signal synchronization as a way to increase capacity without having to widen roads.

In the short run, he says, delays can be reduced, especially during rush hours.

“Over time, however, studies have shown that as the road becomes more efficient, it enables induced demand,” Richter says. “The solution becomes a victim of its own success.”

Reduces energy consumption

The U.S. Department of Energy says on its website that traffic-signal synchronization increase efficiency, reduces energy consumption and eliminates or delays the need for street widening.

DOE also lists “potential disadvantages,” including increased travel speeds and additional traffic.

Reid Ewing, a professor of city and metropolitan planning at the University of Utah in Salt Lake City, says getting traffic-signal synchronization right is one of local governments’ most important responsibilities because it affects almost everyone.

It’s difficult, though, to get it right, he says:

  • Too often, Ewing says, protected left-turn arrows slow the entire system.
  • Cross streets can be given too much time on green lights, slowing traffic on major roads that intersect with them.
  • Traffic engineers don’t always update signal intervals to match changes in volume and flow.
  • To work correctly, signals must be close to each other or at least a quarter-mile apart. The progression of traffic through irregularly spaced synchronized signals isn’t optimal.

The best signal systems, which have been employed for years in Great Britain and Australia, is the one being installed in Minneapolis, Ewing says.

In the “adaptive timing” system, traffic is monitored in real time through “loops” or sensors in the roadway and signal intervals can be constantly adjusted.

More common in the United States, Ewing says, are pre-timed systems with signal timing locked in, and time-of-day timing that changes during peak and off-peak driving times. 

Getting it right is vital not just to smooth traffic flow, but to ease drivers’ stress levels. Poorly timed signals, Ewing says, “grate on drivers, are irritating, a waste of time and a nuisance.”

Other alternatives

Nozzi wishes city planners and traffic engineers would turn more often to alternatives to signal synchronization. He thinks traffic roundabouts are a good idea, though they “create intersections that are too large for pedestrians.”

He’d like to see streets made more bicycle-friendly and more residential development in downtowns so people don’t have to drive as much. And he suggests that streets be designed differently to force drivers to slow down.

“Motorists travel based on their perception of the fastest speed that they feel safe at,” Nozzi says. “The only way to really effectively slow down cars is to design streets to be more narrow and obligate the motorists to be more careful.”

Get MinnPost's top stories in your inbox

Related Tags:

About the Author:

Comments (8)

It's great when we can use

It's great when we can use science and technology (such as traffic signal timing) to improve people's lives.

I know that a majority of Twin Cities citizens do not take public transit, but it should be noted that traffic calming/slowing greatly affects bus travel, also. As a bus passenger, the ride down the stretch of Marshall Ave that has been reduced to one lane each direction has become painful during rush hour. Same with the 16 ride down University Ave now that the road has been narrowed (the bus can no longer pull into right turn lanes/parking areas ahead of stopped traffic for riders to depart or enter- we just wait longer to get to a destination like all tge cars) And as a pedestrian, I do not find congested, traffic calmed intersections safer to cross. In fact, I find a lot of drivers eager to get out of the congestion who pay even less attention to pedestrians.

Safety stats?

Didn't any of these reports comment on whether accident rates (and injuries and fatalities) went down or went up with stop-and-go v.s. more free-flowing traffic?

It would seem to be an important part of the assessment.

We've been doing those things

And hopefully we will continue to add infrastructure to enable biking and encourage more downtown population.

But improving the traffic signals is long awaited necessary upgrade. I moved back to Minneapolis (living and working downtown, and commuting on foot) after just over a decade in DC and could not believe how poorly coordinated downtown traffic signals are. And trust me, driving in downtown DC is no picnic either. Despite very light non-peak traffic, downtown Minneapolis was worse.

There is simply no reason to have to stop at every intersection when trying to get across downtown to, for example, get to the grocery store.

.

This topic interests me, as my goal when I drive is to get from Point A to Point B as smoothly and with as little use of my brake as possible. I'm also very familiar with induced demand & strongly believe that social costs of driving (all the way up to military spending and climate change) should be internalized so that combustion-based travel modes drop significantly & other modes prosper. But it's hard for me to believe that whether lights are timed affects a person's choice to drive or use a different mode. Whether driving is the necessary mode is decided on its merits; then either lights are timed on the route and gas wastage and pollution is reduced, or it is an irritating stumble from red light to red light. I will choose routes specifically to avoid corridors with poor signal timing (yes, Hiawatha Avenue, of course), but it doesn't affect mode choice.

Contrary to the article, I would tend to favor a pre-timed system over an "adaptive timing" system. At least on routes with which drivers are familiar, it is not only the timing, but the knowledge of the timing, that allows for smooth flow. If timing varies due to system feedback, drivers will not be able to anticipate speed and lane movements to match the timing and the benefits will be lost.

Higher Speeds helps with Pedestrian Issues through Attrition!

The biggest overlooked advantage of the new lights-timing is the higher speeds and system efficiency. Now cars can easily reach fatal collision speeds quickly, and keep these speeds for longer stretches. With each pedestrian collision and death, we also reduce the number of pedestrians. We will send a strong message that cars mean business, and that pedestrians better stay off the roads, while reducing their numbers.

Seems like a win-win!

i can cross Lyndale ave in the evening on streets without ....

streetlights. I had done this prior to the redesign. It is now more dangerous. Cars are travelling faster now through a single lane. Calm traffic all you want but if you don't also calm the rush of life we all live in I would debate the traffic calming is an added stressor.

Timing depends

…upon whether the goal is to move traffic powered by internal combustion engines, or traffic powered exclusively by the use of muscles. If the goal is to move cars, buses, trucks, etc., then timing the signals so that traffic flow is enhanced (it'll never be perfect) is — or ought to be — a no-brainer. If the goal is to reduce speed of travel, on the premise that slower traffic makes the streets safer for pedestrians and cyclists, then traffic obstruction in the form of uncoordinated traffic signals is the way to go.

I side with Chuck Holtman on this one. I don't change modes of travel based on traffic speed. Ideally, I'd be able to go wherever I needed to go via public transit, but that's not possible in my corner of Minneapolis. So, once I'm committed to driving, making the task more difficult and time-consuming via uncoordinated signals is plain stupid on the part of traffic engineers.

Lake Street

This will be the true litmus test. Lake Street has the worst traffic lights in the city that ends needless time to cross city commutes.