DaveZ

Yesterday, driving through my neighorhood, as I approached a four way stop, a woman was coming the opposite direction. She blew through the stop sign at 40+ mph.

My first thought was if I had been riding and went right through like I sometimes do, I would never have seen her.

I see lots of riders blow stop signs without even slowing down. Just sayin'

knurly

I usually stop 50' from the 4-way until the intersection is mine. I guess that is why I don't reside in NYC.

unterhausen

Yesterday, I saw a cop drive right through a stop sign and do a panic stop when he saw me. I'm going to laugh at the next LEO that tells me about cyclists running stop signs. I don't understand anyone running stop signs without regard to oncoming traffic. I do understand cyclists running stop signs at speed when they have good sight lines. We have way too many stop signs in the U.S., and most of them are there because people are too stupid to drive.

jack002

Stopping = rolling at like 5-9mph, at least in my world, maybe not for you. Keeping alert and looking around is always a good idea, not just in intersections.

genec

"Without even slowing down;" OK but what is their speed in the first place? I am not condoning running stop signs, but there are a few things we need to consider when comparing that 40MPH automobile running a stop to a cyclist running a stop. First you are right, in the event two stop sign runners meet and one is in a car and the other on a bike, the cyclist loses... every time.

Second the auto is moving at 40MPH and has A pillars and other things that limit visibility... the cyclist on the other hand is moving somewhere between 10 and 20MPH and has no obstructions to either visibility or sound... and likely can see and hear a crossing vehicle before any driver would even notice a cyclist. Again this does not justify a cyclist running a stop... but merely shows that a cyclist is likely to be far far more aware of their surroundings than a motorist, AND due to slower speed, is more likely able to stop in a short distance.

Yup you should slow down, heck, even stop... but the odds are, as a cyclist your slow speed and better awareness of your surroundings may have alerted you to slam on the brakes before being creamed... maybe... just maybe.

Learn to stop... or at least come to a slower roll.

Wilbur Bud

Ignoring the rightness or wrongness of stopping for a stop sign, the periodic debates made me wonder about how long I’m spending each day stopped at stop signs, so I tried to calculate the time.

Considering at a minimum it’s the time to stop plus the time to speed back up to the cyclist’s normal speed, I come up with approximately 6 seconds for myself, including about one second to actually look at the intersection while stopped before proceeding. That based on myself and bike weighing 200 pounds, commuting at a speed of 15 mph, that my maximum sprint power output is constant at 1,000 Watts for the few seconds of startup, and that I can stop my loaded bike at a specified rate consistent with full stop within 15 feet from 10 mph.

I counted my stop signs on the way home last night, looks to be about 20 of them (not including traffic lights – 8 of those). So, my minimum total delay due to stop signs is probably in the range of 2 minutes of my nominal 60 minute commute, for a overall average loss of 3 percent. Probably more than that due to other traffic in the intersections, but that would seem kind of normal to me and not part of any delay induced just by stopping.

Time to stop depends on initial speed and also braking ability. While many State laws still define adequate braking as those that are able to skid the wheels, a few States have laws like “Must be able to stop within X feet from a speed of Y mph.” A brief search says Florida requires 25 feet from 10 mph and Massachusetts requires 30 feet from 15 mph, plus a model State law text requires 15 feet from 10 mph. Using 15 feet from 10 mph as a model I calculate a braking acceleration of -7.174 feet per second squared. But, assuming many cyclists may travel much faster than me, I had a look at the stopping times from typical speeds using that calculated acceleration value (thinking most cyclists could stop more quickly than that if they wanted to do it).Time to speed back up gets a little trickier, because it depends on the weight of the cyclist and bike plus how much power the cyclist can generate, along with what speed is desired. While cycling forums generally talk about “dialing up to 400 Watts” that value is really more of a steady state sustainable output for a top cyclist over a long distance, and getting up to speed from a stop sign is more of a short duration peak or sprinting power output. Given that, the information I found stated that a non-athlete sprinting in 30 second increments on a cycle can generate more like 900 Watts for the short duration, and professional cyclists can generate more like 2,000 Watts peak. For myself, based on that information, I’m going to say I can sustain 1,000 Watts for the 5 seconds or so it takes me to get up to speed.

First step is to calculate how much energy it takes to arrive at my desired speed (ignoring nuisances like friction and wind resistance). Kinetic energy equals one-half the mass times the square of the speed, so ½ (200 pounds/32.2)*22*22 = 1,512 lb-ft. The unit correction constant of 32.2 is due to the USA system of units (feet, pounds, etc.).

Second step is to calculate how fast I can get up to speed knowing my power output. If I weighed less I’d need less energy. The energy is a constant once you ignore wind and other friction effects, but I’m going to assume my full power capability of 1,000 Watts is constantly applied. 1,000 Watts = 738 lb-ft per second once I make the conversion to the US customary system of units. So, when I divide Energy by Power I get (1,512 lb-ft) / (738 lb-ft per second) = 2.05 seconds to get up to a speed of 15 mph when bike and rider weigh 200 pounds and the rider can put out 1,000 Watts for a few seconds.
Those are all calculated values with loads of assumptions, and while they generally match my personal experience on the road, I’d be curious if anyone has ever taken any measurements?

gmt13

First, I think that 4-way stops are stupid. They create a situation where most drivers have reduced their perception of the hazard because "the other driver will stop". 4-way stops promote bad behaviour, which then carries over to other stop situations.

Second, rolling stops are so prevalent around here that you could actually believe that they are part of the driver's test. When I first started running with a video cam, I used to clip out all of the stop infractions with the idea that I would paste them into a collection. There were just too darn many and so I don't bother to clip anymore.

Third, the biggie for me is right-turn-on-red. I've observed that most drivers will slow appreciably to roll through a stop sign, but they RTOR at the same speed they would carry if they had a green light.

-G

Poguemahone

Four way stops are often put in as a traffic calming measure. The traffic they are attempting to calm is automobile traffic, not cyclists. As a traffic calming measure, they are a complete failure. They would be a complete success if they were put in to give motorists complaints about cyclists, as most motorists hold cyclists to a completely different standard than they do drivers (ie. cyclists should come to a complete stop, motorists should cruise right thru).

The silliness of holding cyclists to what is an attempt to calm automobile drivers is pretty stupid, IMO.

unterhausen

I've never done measurements, but I generally come to a complete stop at stop signs. When I ride with people who roll the signs, that often leaves me far behind.

noisebeam

Correct. good information here:

https://troymi.gov/trafficengineering/multiway.htm

mprelaw

In many cases, 4 way stop signs are put there for speed control, not because the intersection is inherently dangerous.

The best one is on the main road leading out of my development to the highway. It's on a 90 degree bend in the road. Not even at an intersection. I honestly question its legality. And BTW--no one---and I mean NO ONE----stops for it. I guess the whole idea is to get people to slow down before the curve---as if they couldn't see the trees behind the yellow reflective barrier with a bunch of >>>>>> pointing out the curve.

SactoDoug

That is what I do. I slow down, look and if there are cars there, I wait my turn or roll through when the car at my sign goes.

noisebeam

Unfortunately they increase motorist speed.

Paul Barnard

It's a very good idea to visually clear any intersection before entering it. Sometimes this can adequately be done by slowing. Sometimes it can be done at 20 MPH. Sometimes it takes a stop and careful study. Stopping doesn't make entering the intersection safer. Visually clearing it does. When these cyclists that you see "blowing" through stop signs do it, what speed would you estimate they are doing and do they appear to check for traffic? To hear some people talk there is a pervasive problem of cyclists "blowing" through stop signs, yet if the accounts of accidents on these pages are an accurate indicator, one of two things is happening. Cyclists are getting damn lucky on a regular basis or "blowing" through stop signs is more of an imagination issue than one rooted in reality.

noisebeam

My two closest avoided crashes were with cyclists blowing stop at speed.

DX-MAN

I'm waiting for a local LEO to stop me for doing something a driver does habitually (that includes the majority of the PD). I won't hold my breath, though -- my BIKE is blue, my face doesn't need to match it.