Posts about Traffic Lights
Roads
Don't expect green lights all the time
You're driving along in downtown DC. You get a green light and start moving, but just as you get to the next corner the light turns red. It's frustrating! But it's no conspiracy. There could be reasons this happens, even besides trying to help pedestrians and cyclists.
Photo by apium on Flickr.
Adam Tuss's latest NBC TV news segment brings the shocking revelation that drivers don't like to stop at red lights, and that at least one person thinks it's another part of the war... I mean, the nonexistent general pattern of DC deliberately pursuing policies that make things worse for drivers.
Tuss read an email on the Tenleytown listserv, by semi-anonymous poster "Paul," alleging that DC deliberately times lights to slow down drivers. Tuss makes this the core of his story, with a response from DC transportation officials who say that this is not true, though actually, they'd really like to install a more modern signal system that makes it easier to time lights.
In the TV news tradition, Tuss also interviews a few "people on the street," and does make sure to talk to people with multiple points of view. One driver thinks DC can probably figure out a better system, though he doesn't say anything inflammatory. Another says it's important to design signals to accommodate pedestrians, adding, "cities are for people, not for cars."
At the end, Tuss and his crew take a drive on Wisconsin Avenue. We can see them leaving one intersection with a green light and getting to another one. He concludes, "Clearly, from the driver's standpoint, some signals were not timed properly."
Actually, no, and this is the most dangerous part of this report because it reinforces the notion that if you hit a red light, there is something wrong with the timing.
Quite simply, lights are not going to be green for everyone all the time. Wisconsin Avenue, for instance, is a 2-way street. Any timing that gives successive green lights to people driving one direction will mean more red lights the other way.
Parts of 16th Street do have "platooning," where lights turn green in succession. This also encourages people to drive the speed limit, since if they go faster, they'll just hit red lights each time. Some people surely think 16th's lights are terrible because they keep hitting red lights. Others, driving the opposite way, have a legitimate beef that they timing makes things worse for them.
Downtown, there are many main streets intersecting at various angles in close proximity. There's no way to time all of the streets for continuous greens in every direction. Should the timing encourage people to drive north on 16th or west on streets like R and U in the evening? Both have a lot of commuters traveling in conflicting directions.
One way to combat that particular problem is to close segments of streets to car traffic. When New York closed the diagonal Broadway around Times and Herald Squares, it found that traffic flowed better because the diagonal confounded signal timings on the avenues. DC could probably help everyone better traverse a place like Dupont Circle if it reduced the number of roads coming in, but that would surely spark even more "war on cars" claims even if it actually helps cars and the people inside as well as pedestrians, cyclists, and bus riders.
There are many other reasons traffic engineers might time lights in a way that appears wrong to a driver traveling a particular direction. Contributor and engineer Andrew Bossi offered many examples, such as:
Gap Provision: Providing breaks in traffic, such as to allow nearby uncontrolled interactions to operate adequately. Without these breaks, some uncontrolled intersections may never be able to clear out, subsequently requiring some treatments such as an additional traffic signalStill, many signals in DC aren't timed with a lot of forethought. DC doesn't have a state-of-the-art system to control all of the lights centrally. Many individual decisions get made based on local neighborhood pressure, the District Department of Transportation (DDOT)'s James Cheeks has told me and others. That can have its pros and cons; sometimes neighbors know well where the trouble spots are, but it also makes the overall system haphazard.— which would only increase motorists' delays. Breaks in traffic improve net mobility for the greatest amount of road users.
Many signal timings could be better. If DDOT changes them, however, it won't necessarily ensure that Adam Tuss always gets a green. What helps move on group of drivers could slow down another group. Also, as people say in Tuss's story, drivers aren't the only people on the roads.
In some places, DC could time signals to help buses get past a trouble spot when they cross a busy road. That might mean drivers on that main road more often get a red, but if the bus caries 20 people and 5 drivers have to wait a little longer, it's a net gain. Pedestrians need time to cross, especially wide roads like Wisconsin in places with a lot of seniors like upper Northwest.
Any fixes to signals have to take everyone's needs into account. That'll surely make someone frustrated, creating good fodder for another Adam Tuss transportation story.
Roads
Instead of tickets, turn lights red for speeders
Opponents of speed cameras often insist that they don't want drivers to speed
Photo from FHWA.
How about wiring radars to turn the next traffic light red whenever a speeder passes? Instead of getting a ticket in the mail, a speeder would just get a red light. With the right settings, this would slow down all speeders Traffic safety experts I spoke with could not point me to any experience with such a system, so it will take trial and error to work out the bugs and optimize the design. Speeders' behavior is more likely to change if they understand why they got the red light, but if drivers get that message too soon, they might speed up more to beat the light instead.
If a light turns green and then a speeder fairly quickly shows up, turning it red again, there might be pedestrians in the parallel crosswalk. They'll need time to finish crossing, which would mean a 4-way red period. However, these will have to be minimal so that drivers are not overly tempted to run red lights.
And how would this work on multi-lane roads when one speeder might stop traffic for many other law-abiding drivers? Signals always give some unnecessary red intervals There shouldn't be legal obstacles. Radar-actuated traffic signals are approved by the Federal Highway Administration, and state laws that limit the placement of speed cameras do not apply to them. Some cities (including DC on parts of 16th Street) already limit speed with traffic signals by synchronizing closely-spaced lights so that drivers who exceed the limit hit a red.
How and where might this strategy work best? And will objections to automated speed limit enforcement diminish when the radar system no longer raises revenue from drivers?
Pedestrians
VDOT was supposed to install signal where pedestrian killed
A traffic signal and crosswalk was already planned for Virginia Route 234 at the very spot a man was killed yesterday. The signal had been promised for spring 2010, but hasn't yet been installed.
Image from Google Street View.
The man was crossing between a McDonald's and a commuter bus lot near Route 1 in Dumfries where Potomac and Rappahannock Transportation Commission (PRTC) buses travel to the Pentagon and downtown DC.
The pedestrian danger there is nothing new. According to TBD, people often cross here on foot. It's not just people eating at the McDonald's; this is the main way to enter the lot as a pedestrian, including when transferring from other buses.
There are no crosswalks at the intersection of 234 and Route 1, and along the side of 234 adjacent to the lot, there was not even a sidewalk until recently. As part of a large expansion of the lot, Prince William County and VDOT planned a new sidewalk along the edge and a signal at the McDonalds/commuter lot entrance on 237.
Image from Google Street View.
The lot has since been expended and the sidewalk added (the bright white line in the above picture), but not the light. According to information obtained by GGW, Prince William officials said in December that VDOT was scheduled to install the signal by the spring. However, installation was subsequently stalled waiting for parts.
WTOP reports that VDOT is now promising the signal by "mid-November." If they had gotten it done within even six months of the promised date, however, Mr. Zelaya-Jovel would probably be alive today. And if a crash were to happen in that spot, Prince William police wouldn't so cavalierly dismiss the issue.
Roads
Pedestrian safety: Fines? Lights? Two-way streets?
Pedestrian safety is barnstorming through the discourse in neighborhood after neighborhood. Last night, residents of Dupont Circle debated making 15th Street two-way. This morning, the DC Council held a hearing on a bill to raise fines for failing to yield to pedestrians. And in Chevy Chase, debate is raging over a special pedestrian signal at Connecticut and Morrison.
Photo by Mike Licht on Flickr.
Even the American Automobile Association, which people join for emergency towing service but has historically used the revenue to lobby against transit and for more and faster roads, wants better enforcement of laws against unsafe driving that create danger for pedestrians. Everyone agrees pedestrian safety is important, but what should we do about it and how far are we willing to go to inconvenience drivers?
The Council's bill would raise the fine above the current $50 for drivers who don't yield to pedestrians. The current rate may be too low, and not enough to make drivers take it seriously. Portland's goes up to $350, and in some spots in Virginia it runs as high as $500. On the other hand, too high a fine would simply generate anger and seem too punitive.
Everyone at the hearing agreed that the most important element is enforcement: the police simply don't ticket people for failing to yield, or for talking on their cell phones while driving, or almost any other moving violation. Some have also suggested assessing points on the license for this infraction.
Meanwhile, last night's 15th Street meeting rehashed many of the same arguments I listed yesterday. Residents continued to be about evenly split on the issue, but most importantly, everyone supported enhancing safety. The real debate was between those who believe two-way would be safer, and those who think one-way is safer. I am confident two-way is safer, but those who feel otherwise disagree on the means, not the ends.
One person proposed an interesting option: signals that are red in all directions, allowing pedestrians to cross in all ways including diagonally, and to do so without competing with turning cars. A signal that's all red both ways while pedestrians can cross is called a "Barnes Dance", and according to those at the 15th Street meeting, downtown DC had these until the 1970s when they were all removed.
DC has only one Barnes Dance type signal, at Connecticut and Morrison that's the subject of neighborhood controversy. DDOT installed this signal last year, replacing a stop sign. Instead of a regular traffic light, this one is blinking yellow on Connecticut (allowing cars to go) and blinking red on Morrison (like a stop sign) until a pedestrian presses a button to cross. Then, the light waits until the lights at neighboring blocks are red on Connecticut before changing to all-red for cars and a walk sign for pedestrians. There's also a "no turn on red" sign to make it clear that during the all-red phase, cars are not supposed to turn right.
This is great for pedestrian safety, eliminating the danger of being hit by turning cars. But some cars turn on the red anyway, so accustomed to being able to turn right on red. Instead of adding better signs to deal with the confusion, many local ANC members are pushing to convert this light to a traditional three-color signal. We should have more pedestrian signals, not fewer, and at the very least should make sure to give this one a shot before scrapping it.
Speaking of right turns on red, those can be a hazard in crowded areas. Should we restrict them? New York City disallows right turns on red, except where a sign specifically allows it. Some residents suggested restricting right turns on 15th Street at last night's meeting. But more importantly, Councilmember Tommy Wells brought up the topic at today's hearing. "We should think about reversing the presumption, where it's only right on red where there's a sign that permits it, rather than the opposite," said Wells. That way, a car would have to stop and ensure there's a right turn permitted instead of assuming as much and rolling through the stop. Wells is indeed the Council's leading advocate for, in his words, "upgrad[ing] the rights of pedestrians to being the same as the rights of cars, at least."
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