Q: It’s obvious that many drivers routinely exceed the speed limit in many areas, not just on freeways. So the next logical question is: How are speed limits determined? One would hope that there is some science, not just politics or customary historical norms, that inform the speed limit decision for a stretch of road.
A: Your hope is not unfounded. The law does set default speed limits for various kinds of roads, which I guess you could say is setting limits based on historical norms, and they’re set in state statute by elected officials, so you could call that politics, but there’s more to it than that.
We don’t build roads however we want and then hope the default speed limit works for them. There are design standards (lots of them) that apply depending on the size and speed of a road. Let’s say that a city road engineer is designing a new road. State law sets the maximum limit for a city road at 25 mph. If that’s what the city needs, the engineer would design a road that meets the standards for that speed limit. But maybe the city has in mind an arterial with higher speeds. The law allows increases and decreases in speed limits “on the basis of an engineering and traffic investigation.” If the road is designed for it, the city could have a higher speed road. Apologies to the road engineers for oversimplifying here, but that’s my layman’s summary.
A speed limit could also change after a road is built. As homes, businesses, and driveways increase along a stretch of road, a city might do a study and decide to reduce the speed limit based on factors that weren’t present when the road was built. The right speed limit is based on more than the design of the pavement; it also includes the surrounding conditions. For example, a road in proximity with lots of pedestrians should have a lower speed limit than a similar road where there’s rarely a walker or bike rider.
There is an exception to the “engineering and traffic investigation” requirement for reducing a speed limit. The law allows local authorities to set 20 mph speed limits on non-arterial roads without a study. You’ll most likely find this applied in neighborhoods.
But setting an appropriate speed limit doesn’t guarantee that it’ll be followed. You’re correct that many people speed, and not just on freeways. Until recently, we didn’t have the hard data to support your observation, but in 2022 the Washington Traffic Safety Commission performed a speed observation survey. It’s just what it sounds like; measure the speed of cars as they drive by and count how many are speeding. The survey covered 206 locations in 30 counties around the state.
The bad news: 76 percent of drivers speed. But it’s also true that not all speeding is equal. Driving two mph over the speed limit is not the same as driving 15 mph over, and researchers have calculated the impact. For every one percent increase in speed there is a four percent increase in traffic fatalities. In Washington, over half of speeding drivers are between one and five mph over the speed limit. While ideally all drivers would respect the speed limit, it’s a small percentage of high-risk speeding drivers causing the greatest harm.
Nearly a third of all traffic fatalities in Washington involve a speeding driver. That’s 270 people in 2023. We could save a lot of lives just by slowing down. This is a call to be better drivers, at least until the robot cars take over.
I think it’s still very political. There was that accident that killed 3 people on 140th in Fairwood this year. After that happened, the speed limit was reduced from 40 to 35, prior to the final study being produced. That was based on input from the “neighborhood,” which apparently thought that a 5 mph speed limit reduction would have prevented an accident where the young driver was going over 100 mph. Total nonsense, but even so the speed limit was reduced despite little or no change in road conditions in the area.
https://kingcounty.gov/en/dept/local-services/transit-transportation-roads/roads-and-bridges/projects-and-programs/traffic-safety-fairwood
Yep, the article is how things generally work, but there are some roads with artificially low speed limits, sometimes, as you mentioned, because of the will of the people. The problem with setting a speed limit lower than the road design is that drivers, especially if they’re not paying attention to speed limit signs, will tend to drive at the speed that feels comfortable. If you build a road with 50 mph standards and set the speed limit at 35 mph, now you have an enforcement problem. If a community wants slower speeds on a road, in addition to changing the speed limit, there should be some design changes. It doesn’t have to be expensive. Just painting the stripes so that the lanes are a bit narrower will encourage drivers to slow down.
I love the subject “speed limits” . They’re the most powerful signs on our highways. In many places it’s why communities have hired policemen. To many drivers the enforcement of those signs have been the most dangerous part of driving. Those of us who obey ( I drive no more than 2 mph over the posted speed limit 99.99 % of the time) the speed limits are punished with time for obeying them. The speed limits are first of all posted for the convieniance of enforcing them, And many times the persons who obey them are almost never respected, or even considered. The question is most always not ask, ( is this speed limit east to obey?) case in point at some roadwork areas the reduced speed is always posted , but it is only optional to post emediately when it ends, so that those obeying the speed limit know exactly when they can get back to the usual higher speed limit. We are punished with time , sometimes for miles until the next posted speed limit. Who fights for our rights as a person who obeys the speed limits, the police, the traffic engineers, the politicians the none drivers. None. It seems sometimes I’m alone in fighting for the rights of drivers who obey the speed limits. The statutory speed limit in some cities has been lowered to 20 mph. On the streets of cities that I drive to I , by law must drive on every street that it looks like it could possibly be a residential street, at 22 or lower mph until I see a sign that says otherwise, to defend myself from traffic law enforcement in that city. Doug are you going to fight for those who obey the speed limits? Many places it’s said to drive with the flow of traffic is the safest speed to drive. I disagree. That would be true if there were no enforceable speed limits , but I cannot and will not drive more than 2 mph over the limit to protect myself from traffic law enforcement, therefore it’s to dangerous for me to drive with traffic if it’s going more than that. Try it sometime for a week or two, to obey the speed limit precisely and you will see why the average driver drives reasonable and prudent. That’s one reason why 76% of drivers are over the speed limit. Driving the powerful speed limit signs is not respected, but punished too many times with rediculously slow speed limits, and the enforcement of those rediculasly slow speed limits. Instead of punishing the drivers who obey them with added time, and punishing the reasonable and prudent driver with traffic citations, maybe it’s time to start punishing those that post rediculasly slow speed limits. There are no consequences for a traffic engineer who posts a rediculously slow speed limit, which effects hundreds if not thousands of drivers Per Day. If you obey these limits like I have to you will see that it’s almost a crime to allow some of these rediculas speed limits to be posted. To obey some of them you will be in direct conflict with not just the 76%, but more then 95% of traffic, and it’s more the fault of those who post such limits, then the drivers.
It really doesn’t matter what the speed limits are 99% of the people won’t obey by the speed limit laws anyways, I don’t even see why it’s so important on speed limit anyways nobody obeys it.
They aren’t obeyed because there’s little to no enforcement due to budget cuts over the years and personnel shortages.