too many traffic signals?

I just finished reading Confessions of a Recovering Engineer by Chuck Marohn of Strong Towns. I’ll have more to say about the book soon. The reading reminded me of a number of things I’ve wanted to write more about, and one of those is traffic signals. Chapter 7, Intersections and Traffic Flow.

“Traffic signals are the most mindless and wasteful thing Americans routinely install to manage traffic. Removing nearly all of them within cities would improve our transportation systems and overall quality of life.”

Chuck Marohn, Confessions of a Recovering Engineer

I have long wondered what the value of traffic signals really is. As a walker, they make me wait for the signal cycle when there is no traffic coming. As a bicyclist, they stop me at almost every location, because they are set for the speed of cars, not the speed of bicyclists. There are places that set signals to work for bicyclists, but nowhere in the Sacramento region. Of course as an enlightened walker and bicyclist, I wait only for gaps in traffic and not for the signal to change. As a driver, which I once was, they make me sit at an intersection when I could be moving, and slow overall travel time.

Most signals do not sense traffic loads and respond. They are on a cycle, no matter what. Rush hour, midnight, same cycle. Signals are timed to preference one direction of traffic over the cross-traffic. And they are often very slow cycles. In the county, many of the signals are on a 2.5 minute cycle, and even in urban areas they are on a slow 1.5-2 minute cycle. Drivers have come to accept the long wait, but for walkers and bicyclists for whom a red signal can increase overall travel time by 1-1/2 to two times, they make us crazy.

Signals do not slow the speed that drivers drive. Drivers wait at the red light, and then accelerate on the green to make up for wasted time, always going over the posted speed limit. Of course these days many drivers don’t stop for red lights at all, they go through intersections on stale reds (meaning it was red before they even entered the intersection). This has become a very common behavior over the years, and is almost routine since the pandemic.

One of the things that signals seem to do is shift unsafe driving behavior from intersections to corridors, the street parts in between signals. Instead of misbehavior at intersections, causing lower speed crashes, we get misbehavior in between, with higher speed crashes.

Everyone who walks knows that signalized intersections are not safe places to cross the street. Drivers turning right look only for opposing traffic, almost never for people in the crosswalk. When the light turns green, drivers accelerate into right hand turns, across the crosswalk and any walkers in it. For intersections that permit left turns on green lights, the threat of a left turning driver crossing the crosswalk at high speed is constant. So people who value their life tend to cross mid-block, where one only has to look for two directions of traffic instead of 12.

The Confessions book suggests several alternatives to traffic signals, including roundabouts, traffic circles, and shared space intersections.

  • Use roundabouts rather than traditional intersections. Of course in place where the size of intersections is constrained by right-of-way and adjacent buildings, a real roundabout may not be possible, but traffic circles, of which the central city already has a number, can fit. Traffic circles are not as effective as roundabouts, but can replace signals.
  • Slow traffic enough that people can cross streets without having to have signals to interrupt traffic.

I realize that many people associate signals and stop signs with safety, and often demand signals and stop signs when the streets are dangerous. So what I am going to say here will be controversial. For people who think traffic signals make things safer, please spend some time observing at both signalized intersections, and unsignalized intersections. Are the ones with signals really safer? For anyone?

One of my (not) favorite signals is at 15th Street & E Street. At this point, 15th Street is not a collector or arterial, it only becomes one-way a block earlier at D Street, and has very little traffic at this point. It does not become a higher volume street until H Street and I Street to the south. E Street is a collector, though not a very busy one. Yet the signal cycles all day long, with almost no traffic at it. A perfect location for a traffic circle. Not the point of this post, but 15th Street at this location does not need two lanes, one lane would be plenty, and the excess lane can be converted to diagonal parking and/or a bike lane. A photo of the intersection is below, showing a typical amount of traffic.

What about all the signals on 14th Street? This is a low volume, fairly low traffic speed street, at all times of day. It dead-ends at the convention center, so it is not really even a through street, yet it has five signals. There are a lot more such examples. You can add yours in the comments!

15th St & E St intersection, Sacramento

All the signals in the central city that are not at the intersection of collector and/or arterial streets should be slated for removal. If the city wishes to do so, it could do a traffic study before removal, or just go ahead with removal, but it should not be leaving these signals in place without action. There are options short of complete removal. Signals could be made into signalized pedestrian crossings, so that when people walking need to cross, they still have (some) protection of a red light. (Some protection. Again, many drivers to not stop at red lights.) Curb extensions can be installed to shorten crossing distances. Traffic diverters (modal filters) can be installed so that only bicyclists have a thru route. And of course roundabouts and traffic circles. At the intersection of two collector streets, a four-way stop might be appropriate. Each intersection is unique, but each one is also a candidate for change that makes travel safer and less frustrating no matter the mode of travel.

I’m not suggesting, at this time, the removal of signals at the intersection of collector and/or arterial streets. Someday.

The map shows these signal locations, with a red X (pdf). The intersections of collectors and/or arterial streets, not marked here, are not being challenged at this time. The purple streets are designated collectors or arterials by the city (part of the Functional Classification System).

signals in Sacramento central city for possible removal

More Sac county nonsense

MUTCD-2012_Figure9C-7The Bicycle Detector Pavement Marking (CA-MUTCD Figure 9C-7, shown at right) is placed to show a bicyclist where to stop so that they can trigger a traffic signal. When installed properly, they prevent the all-too-common scenario where bicyclists cannot trigger signals and must either cross against the red light when a safe gap is available, or wait until a motor vehicle arrives. They are also a clear signal to motorists that there is a reason why the bicyclist is positioned where they are. Of course “bicycles may use full lane” is true approaching any intersection where right turns are permitted, however, most motorists do not know or remember this law unless there is a sign there to remind them. The sharrow serves a similar purpose. However, these markings are often not installed in properly.

Mission southbound at Marconi, bike detector placement
Mission southbound at Marconi, bike detector placement

Here is another fresh Sacramento County mistake, where the marking was not placed properly. On Mission Ave southbound, approaching Marconi Ave, there is a Bicycle Detector Pavement Marking in the bike lane, but not in the regular through/right turn lane. This marking is on new pavement placed in a complete streets project along Marconi from Mission westward to Fulton, and was installed within the last two years. If a bicyclist is to trigger the signal, they have to stay in the right hand edge bicycle lane, where they are at risk of getting right hooked. If they adopt a merge position between the two lanes, where they should be in order to make clear to motor vehicle drivers to either get in front or fall in behind, not beside, then the signal won’t trigger.

The solution is to place a marker in the regular lane, and adjust loop sensitivity if necessary, so that the bicyclist can choose which lane position to use.

green wave

A “green wave” is a traffic signal sequence set so that vehicles will encounter green lights for some distance, so long as they are traveling at the selected speed. A green wave can also be set for bicycle speeds, though it very rarely has been, and never in Sacramento.

To some degree, all signals are set this way, though the degree and distance of sequencing varies widely. Many of the east-west streets in the Sacramento grid have signals set for motor vehicles, and when traffic is not congested, it may be possible to go all the way across downtown and midtown on green lights, for example on J Street. Very few north-south streets are set this way, I can think of only the 15th & 16th couplet, and the 9th & 10th couplet. At intersections with the east-west couplets, these north-south couplets seem to have their green wave broken. Only if the grid spacing and the selected speed calculate out is it possible to have a green wave in all directions. Sadly, many signal sequences in the Sacramento region are set above the posted speed limit, encouraging drivers to speed so that they make all lights.

Continue reading “green wave”