The Physics and the Ethics of the Rolling Stop


In 1982, the state of Idaho legalized the "rolling stop," an adjustment to the rules of the road that lets cyclists treat stop signs as yield signs without becoming scofflaws. Nearly three decades later, the rule has a demonstrated track record of safety, but Idaho is still the only state with such a law. Maybe not much longer. Bike advocates in Oregon are working feverishly this week to gain passage of an "Idaho Stop" law of their own. Via BikePortland, this animation by Spencer Boomhower makes a compelling and visually dazzling case for the idea.

  • Doug

    The video is convincing when it emphasizes the safety factors involved in a rolling stop, but less so when it emphasizes efficiency, which it emphasizes heavily. (And I say this as a regular bike commuter who certainly wants to conserve as much energy during my ride as possible.)

    Technically, it is more energy efficient for an automobile to slow down and roll through an intersection if it is safe to do so, since frequent stops and starts is a good way to waste fuel. But no one would stand for a new law allowing cars the discretion to do this, even in situations where there is no cross or oncoming traffic. (This, despite measures across the country to conserve gas.) I’m afraid that telling drivers, “It’s more efficient for me to treat Stop signs as Yield signs,” would result in a whole lot of responses along the lines of “So what? Eat an extra banana.”

    The cause would be better served it it emphasized the SAFETY reasons for the rolling stop. It can be dangerous for a rider to cross an intersection, and if he has to do it from a dead standstill it can be even more dangerous, as he sacrifices the short amount of time he might have to make it across safely. Cars obviously don’t have this problem, as a quick press on the pedal revs them up to 60 mph in no time. Additionally, if a rider rolls through a stop when it’s safe to do so, he gets out of the way of the larger number of drivers who often converge on an intersection. (Compared with the fewer drivers with whom he might simply share a long stretch of road.)

    Convince drivers that a rolling stop is safer than the alternative and you’ve got a real shot at changing minds. But arguing that it should be allowed because it’s more energy efficient is a semantic argument that sets riders and alternative transportation policy makers up for failure, despite Idaho’s success.

  • Doug,

    When I drive my car I exert 1 or 2 calories to press on the brake and then to press on the gas. For a bicyclist it requires many more. That’s the point!

    Look at the BikePortland Blog if you want to read a more in depth analysis about this. Stopping at 20 stop signs at 12mph uses consumes enough kinetic energy for a cyclist to travel 1 mile!

  • lee

    Andy, the point doug was making is how the debate is framed. Instead of saying that rolling stops should be allowed because it is easier for us cyclists, say that they should be allowed because they are safer for you motorists.

    get it?

  • I get it but there is no evidence of increased safety for motorist that I’m aware, unless you are referring to the reduction in bicycle crashes assumed to be with cars. I really don’t see that as being a motorist safety issue at all.

    I’ve been corresponding with Boomhower via BikePortland and he is looking to make some additions and adjustments to the video. Let him know!

  • In my mind the most convincing argument is from experience, both as a driver and a biker. If you are a good driver and you are at a 4-way stop with a bike, you simply can’t trust they are going to yield to you. They probably will yield if you go into the intersection, but if one time out of a hundred you hit the biker (even if it might be “their fault”) you aren’t going to go into that intersection until you know how the biker is going to behave. Most drivers behave this way.

    So, as a biker, what do you do? You can come to a complete stop. In my experience you have to be 100% stopped before the driver will take the right of way. Then, waiting for the car to go through, you re-mount your bicycle and go through yourself. This sounds like the “right” way for things to happen, but in fact everyone waits a lot longer, the biker puts in way more energy, and if there are multiple cars or you are coming into the intersection at the same time as a car (i.e., you aren’t in conflict) then it actually can become far more confusing. What if you stop and dismount, and the car alongside you takes the right of way? What if you go together and the car alongside you turns, maybe into your path? What if the driver who is crossing wants to be nice, and encourages you to go first? It’s a mess, and this happens more often than not. Unless there’s no opposing traffic at all, at which point the biker has stopped and dismounted for no reason, and expecting a biker to do that is just nonsense.

    In contrast, when everyone engages actively with the intersection, and the biker is allowed to time their passage through the intersection wisely, and drivers and bikers can intelligently negotiate who goes through, it works fairly well. The Idaho stop just makes it clear that the sane way to negotiate intersections with bikes is also the legal way. Without that law, everyone just breaks the law.

    Another aspect is that rolling stops are the only way a bike can efficiently go through residential streets with lots of stop signs. This is better for everyone: more pleasant for the biker, less contention on busy streets, less interaction with fast-moving traffic. If bikes took stop signs seriously, it would just put bikes onto streets that weren’t designed for biking and don’t work well, and would leave everyone feeling more pissed off.

  • As far as energy conservation is concerned, the difference between coming to a complete stop (which is required now at stop signs outside Idaho), and slowing down nearly to a stop (as an Idaho stop would allow, if there’s no cross-traffic) is pretty minor. But if you can keep moving through the intersection, you don’t have to put your foot on the ground, and you won’t wobble through the intersection feeling for the pedals and trying to get back to cruising speed. As Doug says, safety is more of an issue than energy efficiency.

  • Rich Wilson

    I agree with Doug. More energy is wasted by cars coming to a complete stop than cyclists, it’s just measured in gasoline rather than corn flakes. If we’re going to argue “we should be allowed to use common sense and roll through clear visible stop signs to save energy” then the argument would apply at least equally to cars.

  • Doug

    “I get it but there is no evidence of increased safety for motorist that I’m aware, unless you are referring to the reduction in bicycle crashes assumed to be with cars. I really don’t see that as being a motorist safety issue at all.”

    And that’s my point. If the only thing we can say is that rolling stops are more energy efficient for US, then drivers will point out that rolling stops are more energy efficient for THEM. Such an argument almost sets drivers up to say, “Hey, that doesn’t seem fair.” If you do that, good luck getting widespread support for such a law. It will remain a niche policy decision by smaller municipalities, unlikely to gain traction in a lot of places.

    The big question to ask is, what’s the benefit to drivers, bikers, and the community as a whole to a rolling stop law? The video doesn’t make a compelling enough case, especially if you see it through the eyes of a car owner.

  • Another argument for Idaho stops:

    In many places, stop signs are used to discourage autombile traffic on residential streets. Many of these routes would be good for bikes — naturally-occurring bicycle boulevards, you might say — but the stop signs also discourage bicycles; instead, they use arterial streets, where they will encounter very few stop signs.

    In general, I think it’s good — both for bikers’ safety and motorists’ sanity — for bikes to take quieter, lower-stress routes when they are available. Idaho stops would make more of these routes available.

  • christine

    The idaho stop is sillustrated as “anytime there is a pedestrian the rider stops and yield. Plus indeed it doe snto apply to red lights .
    How many intersectiosn do we have in NYC where there no pedestrians and no red light ?

    You get the drift.. This is New York city , not Idaho

  • J:Lai

    Christine, the answer to your question is “a lot”, in particular in the boroughs outside Manhattan.

  • Doug et al. I guess we’ll have to agree to disagree but I do see your point. No one else on the other major blogs (that had posted this video) however, brought up this point.

    Also, this might not be a good idea for Manhattan but may work elsewhere. On my way to work here in New Jersey today I practiced several Idaho Stops, some at speed. But at other stops signs where cross traffic is heavy or vision is limited leading up to the intersection I stop completely. We all do it when its reasonable to do so.

  • al oof

    but ian, even with rolling stops, you come to a complete stop if there are other vehicles around. even when i come to a complete stop, cars get really confused by me. obviously this is an issue of other bikers taking the right of way when it isn’t theirs to take, so codifying 4 way stops for cyclists would be nice. but it doesn’t affect the idea that if i am on a bicycle, at an interesection, going slowly, i should be able to assess whether there is anyone coming and stop or continue accordingly. which is to say, treating a stop sign as yield sign means i -will- come to a complete stop, if there is someone approaching the intersection from the perpendicular direction.

  • zach

    Who defines recklessness?

    What to an adrenalin-primed cyclist seems like nearly a stop and a perfectly safe crossing might seem to a bike-hating bike-fearing cop to be clearly reckless behavior.

    Also, perhaps a lower speed limit for all cars within every intersection? If every car slows to ten mph within every intersection, that intersection becomes inherently safe because everyone is able to yield. That’s the standard at most unmarked intersections in the less developed world.

  • John Deere

    Why is the Idaho Stop the only piece of traffic law reform that Streetsblog thinks about? Talk about an agenda (and a debatable one at that). So it takes a little more energy to accelerate from a stop. Big deal. It will develop your muscles & burn some calories.

    There are other traffic law reforms that are being pursued elsewhere that would benefit cyclists way more, but you don’t hear about them from Streetsblog:
    -minimum safe passing distance laws;
    -laws that explicitly give cyclists the right to full use of a narrow traffic lane (New York State has such a law, New York City is exempted from it).
    -Eliminating discriminatory ‘mandatory use of bike lane’ laws. Despite what you may hear on streetsblog, not all cyclists want to use bike lanes, even if they are physically separated. And such laws are used to harass cyclists.

    How about it streetsblog?


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