Thoughts on the stop sign/yield sign debate
I’ve spent a lot of time thinking about stop signs in the past two years, and about how they work for bikes versus cars. In the comments section Alli pointed to this excellent article, which discusses the physics behind the problem that bikes have with stop signs. From the article:
Bicyclists can work only so hard. The average commuting rider is unlikely to produce more than 100 watts of propulsion power, or about what it takes to power a re a d i n g lamp. At 100 watts, the average cyclist can travel about 12.5 miles per hour on the level. When necessary, a serious cyclist can generate far more power than that (up to perhaps 500 watts for a racing cyclist, equivalent to the amount used by a stove burner on low). But even if a commuter cyclist could produce more than a 100 watts, she is unlikely to do so because this would force her to sweat heavily, which is a problem for any cyclist without a place to shower at work.
With only 100 watts’ worth (compared to 100,000 watts generated by a 150-horsepower car engine), bicyclists must husband their power. Accelerating from stops is strenuous, particularly since most cyclists feel a compulsion to regain their former speed quickly. They also have to pedal hard to get the bike moving forward fast enough to avoid falling down while rapidly upshifting to get back up to speed.
For example, on a street with a stop sign every 300 feet, calculations predict that the average speed of a 150-pound rider putting out 100 watts of power will diminish by about forty percent. If the bicyclist wants to maintain her average speed of 12.5 mph while still coming to a complete stop at each sign, she has to increase her output power to almost 500 watts. This is well beyond the ability of all but the most fit cyclists.
We decided to test these calculations on an officially designated bike route in Berkeley, California Street. The street is about 2.25 miles long and nearly flat (average grade 0.5 percent). Traffic is very light, which is nice for cyclists. But California Street has 21 stop signs and a traffic light. More than two-thirds of the route’s 31 intersections require a stop—that’s one every 530 feet. A parallel route, Sacramento Street, runs one block west of California Street. Sacramento has four lanes of traffic and can be very busy, especially during rush hours. With cars parked along both sides of the street, Sacramento has little room for cyclists. But it has only eight traffic lights along the section parallel to California’s bike route, and no stop signs. Since, on average, only half the lights will be red, there ’s only one stop every 2,800 feet.
One of us (Joel Fajans) found that keeping exertion constant1, he could ride on Sacramento at an average speed of 14.2 miles per hour without straining. At the same level of exertion, his speed fell to 10.9 mph on California if he stopped completely at every sign. Thus Sacramento was about 30 percent faster than California. By increasing his exertion to a fairly high level, his average speeds increased to 19 mph on Sacramento and 13.7 mph on California, so Sacramento was then 39 percent faster. While a drop of a few miles per hour may not seem like much to a car driver, think of it this way: the equivalent in a car would be a drop from 60 to 45 mph. Because the extra effort required on California is so frustrating, both physically and psychologically, many cyclists prefer Sacramento to California, despite safety concerns. They ride California, the official bike route, only when traffic on Sacramento gets too scary.
These problems are compounded at uphill intersections. Even grades too small to be noticed by car drivers and pedestrians slow cyclists substantially. For example, a rise of just three feet in a hundred will cut the speed of a 150-pound, 100-watt cyclist in half. The extra force required to attain a stable speed quickly on a grade after stopping at a stop sign is particularly grating.
Exactly! Other things to keep in mind:
1. Bicyclists tend to enter every intersection with caution, whether they have a stop sign or not, because cars often do not see us. We slow down, and sometimes stop, far more often than cars do at intersections where we already have the right of way. We are far more alert than drivers (see No. 2).
2. Bicyclists have tremendous built-in incentives to be cautious at intersections. We won’t suffer a fender-bender if hit–we will very possibly die or be severely injured.
3. Bicyclists can see and hear far better than drivers because we don’t have blind spots and we are not encased in glass and steel. Also, simply being on the bicycle, out in the open air exercising our bodies makes us more alert and more mentally present in our surroundings.
4. A bicyclist’s eyes and ears are some of the first things to enter an intersection. A driver may not be able to see an intersection clearly until the front of his vehicle is six or eight feet into the intersection. In such a case, by the time a driver can see, he is already risking getting hit.
5. A driver is constrained by the road and by the size of his vehicle as to where he can be when he approaches an intersection. A cyclist can maneuver her bicycle sideways in the lane to see more clearly and hear more clearly, often long before she reaches the intersection.
6. As the above article points out, stops signs are a tremendous disincentive to cyclists, causing them to choose dangerous arterials that only disrupt drivers more and endanger the bicyclists.
7. The rear-view mirror and two front corner blind-spots in every car are in precisely the worst place for determining whether an intersection is safe to drive through. This alone argues strongly for making otherwise safe intersections require a stop for a car. But bicycles do not have these problems.
We all know that some bicyclists, usually young, inexperienced ones, sometimes fly through stop signs. The proposed law does not legalize that behavior. It requires bicyclists to enter intersections with appropriate caution.
What the proposed law does is recognize that there are important, fundamental, physical differences between a bicycle and a car, and some of our traffic laws need to accommodate and recognize those differences. Some already do, of course — bicycles are not required to have brake lights or turn signals, for example, even though some marginal increase in safety would probably accrue if they were. Bicyclists in Arizona also cannot lawfully be ticketed for driving too slowly, as cars can. Bicyclists are allowed to ride on the shoulder, but cars are not.
We already have different laws for bikes and cars where it makes sense to do so. If we want to encourage people to ride bikes, and if we want to encourage them to ride in safe places, then Rep. Patterson is right: this is a “fair, common-sense bill.”
–Erik Ryberg
February 11th, 2009 at 7:01 pm
Yea that was a good link.
Motors want to arrive with an overall time.
Bicycles want an average speed.
February 12th, 2009 at 2:22 pm
Erik stated:
“It does not mean bicyclists can “blow through” stop signs. It means they must slow to a safe speed before proceeding through them.”
_____________________________
An LEO needs some metric to use as a foundation to cite a bicyclist who “blows through” a stop sign. The “slow to a safe speed” is too ambiguous. Officers’ judgments will vary; unlike when there is a STOP sign (means to stop fully and it is unambiguous) and a speed limit sign (meaning to stay below a measurable limit of the allowed top speed).
What measures of violation will LEOs have to write citations to bicyclists who abuse this law?
February 12th, 2009 at 3:36 pm
This example gives the rider aobut a 1.25 minute advantage per mile advantage gettting to some location. Just the street for the test is about 4 minutes faster. My bike commute is just about 45 minutes using the faster roads for a good portion of the trip. I’d save 15 minutes by car (assuming no accidents on the route). Some of my choice is the way bike routes are set up going from city to city. A bike boulevard ends in a maze. Car drivers wouldn’t accept that kind of treatment. Cyclists should beable to have fast and ssafe routes also.
February 12th, 2009 at 3:54 pm
Changes in ARS and changes in TPD performance and behavior (institutional change, remember?) are all well and good, but does the frenzy distract from fundamentals such as workable change in the infrastructure?
February 12th, 2009 at 8:35 pm
Ron–
I agree with you half way. This law will discourage law enforcement from ticketing cyclists for “blowing through” stop signs, and some scofflaws are going to take advantage of that, albeit at their own peril.
But remember there are right now yield signs all over the country that have the same rules. This does not invent new rules, it just extends old rules to some new places.
And believe me, I spend enough time in City Court defending bicyclists who get traffic tickets to know that if a police officer makes an allegation in court that he saw a person break the law — a rolling stop, a dangerous turn, failure to yield, riding up a sidewalk to hit the light button — the defendant will be found guilty. The burden of proof is low enough in such situations that a somewhat credible allegation by a police officer reading his notepad will do the trick.
–EBR
February 13th, 2009 at 7:24 pm
“The burden of proof is low enough in such situations that a somewhat credible allegation by a police officer reading his notepad will do the trick.”
Erik, would this not open the door to additional, potentially unjustified, and biased LEO indiscretions against bicyclists? You and I both know that today’s LEOs can be the most abjectly dishonest people among any professional group.
“C. The driver of a vehicle approaching a yield sign and any person riding a bicycle approaching a yield sign or a stop sign shall slow down in obedience to the sign to a speed reasonable for the existing conditions and shall yield the right‑of‑way to any vehicle in the intersection or approaching on another highway so closely as to constitute an immediate hazard during the time the driver or bicycle rider is moving across or within the intersection. “
“ If after driving or riding past a yield sign or stop sign without stopping the driver or bicycle rider is involved in a collision with a vehicle in the intersection, the collision is prima facie evidence of the driver’s or bicycle rider’s failure to yield the right‑of‑way. END_STATUTE”
What concerns me most is that there is no real measure of wrongful actions until ‘after’ a collision occurs (prima facie evidence). Is there no logical, legally binding language available to ‘gauge’ bicyclists’ noncompliance of yielding to another vehicle, pedestrian, or approaching an intersection at an acceptable rate of speed short of a potentially life-threatening accident? As an attorney who has abundant experience in this area—both as a staunch bicyclist and one with a specialized legal practice—you, if anyone, could add to this proposed law’s clarity.
There will always be those bicyclists who would ruin freedoms for the majority by abusing this law. If there was clarity with defining the elements of the law to negate some of the subjectiveness; e.g. slow down in obedience to the sign; and a speed reasonable for existing conditions, then people such as I would likely accept the proposed law.
Several of the bicycles I owned over the years had speedometers. Sans a speedometer, is there a reasonable manner for an LEO located across an intersection or behind a bicyclist to estimate the speed of a bicycle, say, at 5 miles per hour? Since stopping at a STOP sign is what a bicyclist dreads the most, why not set the approach speed at a measureable level of 5 miles per hour —by a speedometer if a bike was so equipped or from an estimated speed discernable by an LEO. At least there is some metric for a reasonable and fair judgment. As a former LEO, I see a requirement for such a speed guide for rendering an equitable and unbiased decision as to the intent of a bicyclist to either yield at a STOP sign or not.
A fast walking speed is 5 miles per hour; after that, most people tend to jog. So instead of writing a statue with statements such as slow down, reasonable speed, then state instead—for bicyclists only: when approaching a bicycle yield sign (motor vehicle STOP sign) a bicyclist must slow to 5 miles per hour, which is approximately equivalent to a fast walking pace. With a reasonable and readily discernable measure, we would all know that “blowing through a stop sign,”—that is, literally running through it in pedestrian terms—was a clear violation of the Bike-Yield law.
A rate of 5 miles per hour will give the bicyclist the full opportunity to survey the intersection safely. A discernable, established speed would lessen the ire from motorists against abusing bicyclists if there is no limit whatsoever, or with varying speeds that are open to each bicyclist’s judgment of what is safe for him/her, and it would lessen the ability of LEOs to abuse their discretionary judgments of what constitutes a yield violation. I would support the Bikes Safe Yield Act if it codified a 5 miles per hour speed requirement during a bicyclist’s approaching a vehicle STOP sign (Bike-Yield sign) and written in the appropriate and unequivocal legalese all vehicle operators can understand.
Thank you for your discussion and reply.
February 14th, 2009 at 9:29 am
“…for bicyclists only: when approaching a bicycle yield sign (motor vehicle STOP sign) a bicyclist must slow to 5 miles per hour, which is approximately equivalent to a fast walking pace.”
For specificity, the statement should read: slow to 5 miles per hour *or less*… or slow to a *maximum speed* of 5 miles per hour…or whatever is most unmistakable.
February 17th, 2009 at 11:26 am
Finding the quickest, shortest way to get
from point A to point B isn’t particularly
a bicycle perspective – it is a car
perspective. Sometimes riding a bicycle
isn’t just about riding a bicycle. It is
difficult in our culture to maintain a
broader focus on how the behaviors we
choose to employ represent the way we
wish to be. WHAT DID HE SAY?..Read it
again.
The BAC spent a good deal of time on this
proposed rule change in its last meeting
and was split on its benefits. Being
sensitive to any future legislation, it
was hesitant to reject the change even
though the reasons for rejection were
plausible. Cavalier attitude of cyclists at
intersections would very likely increase
and that image is something the BAC cannot
bring itself to endorse. Laws respresenting
the way things actually exist, however, only
seem to be in line with cyclists’ desire for
parity on the road, even if that means
different rules for various users. The BAC
could take no stand on this and that is a good
thing because how we use the roads is a work
in progress and as yet remains to be determined.
February 17th, 2009 at 11:59 am
“Cavalier attitude of cyclist”
Convenient statement like lumping church goers with prisoners and expecting everyone to bring a potluck and get along. When it doesn’t happen point out only the bad things and conclude with a bias for the whole group in question.
February 17th, 2009 at 4:02 pm
“Cavalier attitude of cyclist” sounds pretty accurate, actually. Based on personal observation on the 3rd St. bikeway in particular with lots of UA bike traffic, I’d say less than one in twenty now stop for stop signs when there is no cross traffic, and probably at least a fourth blow off the sign even when there is cross traffic that has the right of way. Just last Thursday morning I was just in front of at least a dozen riders approaching a 4-way stop on that route that had cars waiting on both sides of the cross street – as I braked to stop at the intersection I was nearly rear-ended as the whole group, apparently surprised that anyone on a bike might actually obey the law, streamed around me to blow off the sign in spite of the fact that the two cars had the right of way. The people in the “real vehicles” are never going to take us seriously as traffic as long as we keep riding like a bunch of kids on toys.
February 17th, 2009 at 4:06 pm
… and this legislation accomplishes nothing but to decriminalize the act of riding like a bunch of kids on toys, and further widens the public perception credibility gap between our “toys” and the “real vehicles.”
February 17th, 2009 at 4:08 pm
Well, what exists just exists
whether one takes it personally
or not. The obtrusive stand out…the
courteous fade into the crowd. We
don’t need to form an opinion on
things that suit us, whereas an
affront begets an instant bias.
What changes the most with the new rule?
Drivers will be a long time until
knowing “these bikers are ‘blowing’ the
stop signs” legally.
February 18th, 2009 at 12:49 pm
[...] Tucson Bike Lawyer has some great commentary regarding an article on the physics behind the trouble cyclists have with stop signs. Here is a bit from the original article and some commentary from TBL below…and comments from me below that. Bicyclists can work only so hard. The average commuting rider is unlikely to produce more than 100 watts of propulsion power, or about what it takes to power a re a d i n g lamp. At 100 watts, the average cyclist can travel about 12.5 miles per hour on the level. When necessary, a serious cyclist can generate far more power than that (up to perhaps 500 watts for a racing cyclist, equivalent to the amount used by a stove burner on low). But even if a commuter cyclist could produce more than a 100 watts, she is unlikely to do so because this would force her to sweat heavily, which is a problem for any cyclist without a place to shower at work. [...]
February 18th, 2009 at 12:58 pm
I have never heard a description of cycling that sounds more unpleasant. While I understand the writer’s intent, it makes cycling sound so unappealing.
I haven’t driven a car in more than 25 years. When I did drive, I remember feeling like I was riding around in an iron maiden with small windows. I hope I never have to drive, unless I get a version of the pope-mobile.
I live near one of the weirdest intersections in town – Stone and University. Every single day cars take extreme advantage of traffic law there. Left turns on red lights are daily occurrences. What makes cars do that in this intersection and not in others? I am surprised that no one has been killed at this intersection. I have been hit by another cyclist at this intersection.
February 24th, 2009 at 4:36 pm
[...] As might be expected, this proposal is quite controversial, see e.g. the discussion over at tucsonbikelawyer.com, here, here, and here. [...]