Portland Wants to Rethink Speed Limits By Factoring in Walkers and Bikers

Portland wants to change the speed limit on North Weilder Street from 35 to 25. Photo: Google Maps
Portland wants to change the speed limit on North Weidler Street from 35 to 25 mph. Photo: Google Maps

For cities trying to get a handle on traffic fatalities, dangerous motor vehicle speeds are an enormous problem. Once drivers exceed 20 mph, the chances that someone outside the vehicle will survive a collision plummet.

But even on city streets where many people walk and bike, streets with 35 or 40 mph traffic are common. Cities looking to reduce lethal vehicle speeds face a number of obstacles — including restrictions on how they can set speed limits.

State statutes usually limit how cities set speed limits. In Boston, for example, the City Councilhas voted numerous times to reduce the speed limit to 20 miles per hour, but state law won’t allow it.

Now Portland is taking on this problem. A pilot program expected to be approved by the Oregon Department of Transportation proposes a new way to evaluate what speeds are appropriate for urban areas.

The Portland Mercury reports that city officials are challenging the “85th percentile rule,” the old traffic engineering practice of measuring travel speeds on a street, then setting the speed limit at the rate that 85 percent of drivers do not exceed.

One of the problems with this practice is that it doesn’t even consider the presence of pedestrians or bicyclists — only the speed at which drivers travel. The whole exercise can simply reinforce and legitimize dangerous driving speeds on poorly designed streets.

Portland has proposed to reevaluate speed limits according to a matrix of factors that account for motorists’ proximity to walkers and bikers [PDF]. On streets with unprotected bike lanes, for instance, the maximum limit would be 30 mph, for instance, and the same would go for streets with sidewalks on each side. (Roads with sidewalks could still be signed for 50 mph, but only with an “impenetrable separation barrier” to protect pedestrians.)

In practice, the rules would mean that a street like Willamette Boulevard, where the 85th percentile speed is 41 mph and the speed limit is 35 mph, would be signed at 30 mph.

Street design is a more important safety factor than speed limit signs, of course, but lower speed limits can still send a signal to motorists to proceed more cautiously — and they can set expectations for traffic calming redesigns in the future. If the speed limit is 30 mph but motorists consistently go faster, the design clearly needs to change.

On that score, other cities have taken more ambitious steps than what Portland is considering. New York City recently made 25 mph the default speed limit on its surface streets. And the “Total 20” campaign in the United Kingdom has enacted blanket 20 mph speed limits in some towns.

But Portland is turning the tables on the car-centric 85th percentile rule and devising a system that’s more sensitive to the needs of people walking and biking.

And it looks like the city will be able to get its idea approved. State Traffic Engineer Bob Pappe, who needs to sign off on the proposal, told the Mercury, “I think in a city like Portland that’s probably very, very appropriate.”

29 thoughts on Portland Wants to Rethink Speed Limits By Factoring in Walkers and Bikers

  1. “Street design is a more important safety factor than speed limit signs, of course, but lower speed limits can still send a signal to motorists to proceed more cautiously”

    It’s certainly hard to go faster than the vehicle in front of you that does follow the speed limit regardless of design. Of course that person can also infuriate the person behind them so when the would be speeder can get around they’ll floor, increasing risk. But I think overall it helps.

  2. They should measure pedestrian and bike traffic and include them in the calculation of the average! 😀

  3. I was thinking the same thing! Its not crazy but makes a lot of sense. It would result in a lower speed where there are a lot of pedestrian and bicyclists around.

  4. In many European countries the speed limit is at 30 km/h (anout 18 mph). Not always respected, but there nonetheless. I Am appalled how 35 or 40 mph could be the norm

  5. I’m encouraged that Portland is taking this step. Having leadfoot drivers dictate speed limits seems backwards to me – and certainly not safe for ped and bike traffic.

  6. I at first thought of that as a useful method, but then realized that it doesn’t quite make sense. The point of the 85th percentile rule is to set the legal speed for a street at the point that drivers will naturally go based on the design, recognizing the idea that design is really what sets speed with the legal limit just being a codification of this already-existing physical and psychological structure.

    People on foot and bike don’t have our speed affected by design of the street in quite the same way. Thus, once you start including us, the 85th percentile rule no longer recognizes the role of the physical structure and psychological realities in setting automobile speed, and switches over to the idea of a legal limit setting speeds. Once you’re using the legal limit to set speeds lower than the speed that the roadway design encourages drivers to travel at, you might as well just give up on using actual travel speeds. Thus, we get the proposal mentioned here of using features like presence of a bike lane or a sidewalk as part of what determines the speed limit.

  7. The problem is that speed limit signs don’t exist on every block, and they’re often quite hard to see amid the clutter of everything else that exists around a street in a city (particularly if you have flashing walkways with beg buttons, and “share the road” signs for bicycles, and other cosmetic changes that don’t involve real redesign for people on foot or bicycle). Thus, even people who want to follow the speed limit usually estimate the speed limit based on what the street looks like, and not based on any official signs.

    Maybe some day cars will have intelligent navigation systems that can look up the speed limit on every roadway segment from official municipal data, and display that speed limit inside the car even when signs aren’t visible outside. But until then, speed limits have less of an effect on driver speeds than roadway designs.

  8. Right on the concept, but it’s worth noting that the default speed limit is 50 km/h and that usually only applies to cities. It also isn’t terribly uncommon to find roads that are signed higher, they generally are not residential/commercial areas.

  9. This sounds like a crude stab at the Dutch policy of Sustainable Safety. Portland would do well to just go ahead and adopt it in its entirety (with local tweaks as appropriate) as it will greatly improve safety. However, even if they don’t, the city should definitely follow up the newly-lowered speed limits with a program to redesign the streets to reflect the lower expected speed of the thoroughfare. That should be at least done with flexible bollards, striping, etc. immediately after the speed limit change and create a budget program to rebuild the street to the new configuration as money comes available.

  10. Social Justice Warriors to the rescue!!!!

    Making sure that politically correct issues that make almost no difference to 99.9999999999999999% of the population gets all of the attention.

  11. SJWs are pretty easy to pick out of a crowd. They’re the ones who are offended by anything and everything in this world.

    What’s a “rush limbaugh gamergate fiction”.

  12. Nah, crackers like you are easy to pick out of the crowd – AM radio full of hate and offense at anything at everything.

    That said, nothing wrong with being a fighter for social justice. Carry on trollin’ in Maspeth or Mill Basin or wherever you are!

  13. Also, if you have a local police force that rarely enforces speed limits, except in spots where the risk to safety is lower (but it’s easier to hide), a speed limit sign doesn’t mean much.

  14. When you artificially set speed limits lower than what drivers drive and the road is designed for than everyone will be less safe. Eliminating the need for the 85th percentile will create a chaotic city center of increased traffic congestion and road user frustration. Not a good idea! Vision Zero is a social engineering program that is good for only a small minority of road users.

  15. I disagree that ignorance is likely to be a significant issue. If you were to freeze all traffic at any given instant in time and obtain truthful responses from all the frozen drivers, I suspect a large majority of them would know the speed limit of the road upon which they were traveling.

    For instance, every place that I drive regularly I know the speed limit off the top of my head, and I know exactly where the speed limits change. And the vast majority of my driving miles occur on roads that I’ve driven many times previously. When I use a road unfamiliar to me, I might not know the speed limit, but such roads make up a small percentage of my driving.

  16. You mean those who are dying?

    (I agree with your view on speed limits that don’t match road design, but let’s not equate that to Vision Zero!)

  17. When the posted speed limits are significantly lower than the speeds most drivers find to be safe and comfortable, safety is usually decreased. This is a very common result in cities that say they are working toward Vision Zero, but will not spend the money to change the actual engineering of the streets so that most drivers feel safe and comfortable only at speeds lower than before the engineering changes.

    Example: If 85% of the drivers are at or below 35 mph, then posting 35 as the limit almost always produces the best safety and the smoothest traffic flow for all users, including pedestrians and cyclists. Posting 25 in this area, without changing the engineering so that 85% of the drivers now feel safe and comfortable only at speeds up to 25 mph will usually decrease safety overall by increasing speed variance and disturbing the smooth and predictable traffic flow.

    Adding a few speed cameras in such a city is about money, not safety, because unless the cameras are so pervasive that it is impossible to avoid tickets – the overall traffic speeds do not change very much. The problem with pervasive speed cameras, say every block or so, is that then the very expensive cameras lose money and cities won’t use cameras at a loss.

    Engineering is the only real solution, but it is quite rare.

    James C. Walker, National Motorists Association

  18. 50 kph or 31 mph is the default city limit in most places.

    James C. Walker, National Motorists Association

  19. True, but rarely done. Most cities prefer to set artificially low limits that actually reduce safety and then make money with speed traps and speed cameras.

    James C. Walker, National Motorists Association

  20. Overall it decreases safety because only a tiny % will obey artificially low limits.
    James C. Walker, National Motorists Association

  21. I just don’t understand why the speed limits on interstates here in CT are not enforced, especially for tractor trailer trucks and even more so for school buses. I have seen buses with kids on board going 75 mph in a 50 mph posted area. One time I reported it by calling 911 to report the unsafe practice I was told “Please stay away from the bus”! Another puzzle is the determining the “why of an accident” on urban roads. Like when a single car crashes into a tree or utility pole and reporters tell us “the cause is under investigation”. Gotta be that those dang tress and poles jump out into the middle of the road and then as quickly move back to side taking the vehicle with it so as not appear the bad guy. It’s the same everywhere; whatever the speed limit is most (if not all) will go faster. I remember being told by a state cop long ago that “our department can be economically self sufficient just by the fines we issue for speeding”. But as more of them retired and the hiring freeze prevented reinforcements, there just aren’t enough to go around. One last thing: radar detectors should be banned everywhere. Why is it okay to defeat the purpose of speed limits by using them to know when to slow down to avoid being caught? I find the advertisements against drunk driving of texting while driving to be humorous; “Drive sober or get pulled over”, and “You drive, you text, you pay”. Both of these situations must be observed which is not always easy to spot. But a bus going 75 mph in a posted 50 mph area, isn’t hard to miss.

  22. What you people are saying is that speed limits make drivers slow down. No, that’s proven to be untrue. Drivers drive as fast as they feel comfortable. A speed limit is just a number on a sign. What really needs to be done is changing the design of streets, which Mayor DeBlasio of New York City won’t do. This makes drivers slow down, as a faster speed no longer feels comfortable. Some accidents are not the driver’s fault. Is it their fault that a pedestrian leaped out in front of their car? No. Vision Zero shouldn’t focus on only drivers, and they make the assumption that people hit the pedestrians at the speed they were driving at, but people usually slow down by at least a few MPH before impact. Those few MPH could be a life saver. Artificially low speed limits are not the answer.

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