There has been an ongoing debate in my area's local newspaper, regarding biking with vs. against the flow of traffic. A recent incident in which a cyclist was hit from behind, and later died of his injuries, prompted a letter in which another local called for cyclists to bike opposing traffic, so that they could more easily see oncoming traffic and avoid it if a crash was imminent.

Experience, the law, and common sense all say that this is wrong — one would think that everyone knows you should ride with traffic because vehicular cycling is safer. That being said, the debate so far has been almost entirely focused on what the law says, and anecdotal evidence, which isn't enough to convince some people. Does anybody have any references to scientific studies showing actual data on the safety of riding with vs. against traffic? Explanations of why are welcome too, but please include some references or data. I'd like some sources that I can cite in a response showing that cycling with traffic is safer for everyone.

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    You can search around in the FARS/NHTSA/DOT statistics and actually pull all the crash reports for fatalities involving a cyclist going the wrong way. However, I don't believe there's any solid data about what percentage of cyclists ride the wrong way.
    – freiheit
    Commented Apr 16, 2012 at 2:14
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    While your title seems objective and that you're generally open either way, "I'd like some sources that I can cite in a response showing that cycling with traffic is safer for everyone." sounds like you've already made up your mind, the answer is definitively with traffic, and you only want sources that back up your predisposed confirmation bias.
    – Ehryk
    Commented Apr 17, 2012 at 8:01
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    @MountainX check out some of the answers below... it's a lot more dangerous.
    – nhinkle
    Commented Apr 17, 2012 at 18:45
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    @MountainX then you're being selfish. You're putting others at risk, too. Just this morning I almost collided head-on with another cyclist who had the brilliant idea to go the wrong way down the bike lane. He barely had room to swerve around me, and nearly got hit by a car. Have you considered using a mirror to help you see approaching traffic from the rear?
    – nhinkle
    Commented Apr 17, 2012 at 19:32
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    These comments are starting to get fairly chatty. Try to keep comments about improving the question or help with answers and not try to debate the merits of which way to cycle in the comments here.
    – freiheit
    Commented Apr 18, 2012 at 17:37

11 Answers 11


I found this article which has some statistics on accidents involving wrong-way cycling:

Table 4. Against Traffic Compared to With Traffic

[Italics: Against traffic. Bold: Increased risk when against traffic.]

Category Bicyclists
Risk Bicyclists
Risk Risk
All bicyclists 423 33 2.6 2553 56 0.7 3.6 ≪0.00001
Roadway 108 5 1.5 1897 43 0.8 2.0
Sidewalk 315 28 3.0 656 13 0.7 4.5 <0.00001
[Age] ≤17 298 19 2.1 1135 11 0.3 6.6 ≪0.00001
[Age] 18+ 125 14 3.7 1418 45 1.1 3.5 0.0001
Female 118 9 2.6 734 13 0.6 4.3 0.001
Male 305 24 2.6 1819 43 0.8 3.3 <0.00001

Table 4 shows that all categories of bicyclists traveling against the direction of traffic flow are at greatly increased risk for accidents—on average 3.6 times the risk of those traveling with traffic, and as high as 6.6 times for those 17 and under. This result is readily explained: because motorists normally scan for traffic traveling in the lawful direction, wrong-way traffic is easily overlooked. To give only a single example, a motorist turning right at an intersection scans to the left for approaching traffic on the new road, and cannot see or anticipate a fast-moving wrong-way bicyclist approaching from the right.

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    OK, I stand corrected -- there actually ARE some halfway decent stats available. Commented Apr 16, 2012 at 11:34
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    Very interesting! I like how this one shows the actual # of accidents vs. # of cyclists observed, which is what the other data lacked.
    – nhinkle
    Commented Apr 16, 2012 at 15:43
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    @nhinkle -- Of course, the "observations" and "reporting" were no doubt done in entirely different circumstances, rendering the data less than robust. But it's the only port in the storm, apparently. Commented Apr 17, 2012 at 18:38
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    Don't forget that most, maybe all, experienced cyclists would ride with traffic, so those riding against are likely to be systematically different. Less skilled, less experienced, maybe less sober.
    – JKP
    Commented Apr 17, 2012 at 21:15
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    From a Physics perspective, the impact when you drive into a car is going to be higher than when you drive in the same direction and get pushed and roll over the road. Of course that doesn't include the magic moments where you survive by flying over a car or suffer by landing under a car. It should also be noted that when you drive towards the car that he has less time to notice you than when you drive away from the car; so, he has more time to make the necessary corrections, although that doesn't count in that you can no longer make corrections. Commented Jun 5, 2012 at 22:01

For one thing, if you cycle with traffic the closing speed between car and bike is the DIFFERENCE in speed between the two. If you're doing 20mph and the car is doing 45, the closing speed is 25. Reverse it and the closing speed is 65 -- over twice as fast. This affects the time the driver has to react to the cyclist's presence -- over twice as much time to see the cyclist, slow down, plan to pass, etc.

Another thing: If you cycle with traffic and the car behind you does not have room to pass he need only slow down to your speed until the way is clear. If you're riding against traffic there's no real option for him to slow down until it's clear to proceed. In practical terms, this means that in the first case the driver will very likely wait until it's at least halfway safe to pass, while in the second case even a relatively tame, careful driver is apt to try to scoot past somehow, even if there is not safe clearance.

And, combining the two, if it's not safe to pass the driver can slow down just a little, from 45 to 35, say, and cut his closing speed to 15mph, giving him a much longer time to work out a passing strategy. Going the other way, slowing 10mph reduces closing speed from 65 to 55, not a significant change.

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    This is an excellent common-sense argument. Without stopping completely (which is potentially dangerous for the driver), there's literally no way for an oncoming car to avoid passing you if you're riding against traffic. Slowing and tailing the bike until passing is possible, while annoying for both motorist and rider, is infinitely safer.
    – jscs
    Commented Apr 17, 2012 at 23:28
  • I can only agree with this. For the first stretch of my commute this would be either a 30mph difference or a 90mph one (busy narrow downhill 60 road).
    – Stu Pegg
    Commented Jun 6, 2012 at 11:33
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    As a driver, this. If the road is too narrow, it's the difference between gently braking to trail the cyclist and slamming on the brakes to come to a full stop.
    – RomanSt
    Commented Apr 20, 2014 at 11:47
  • And in addition, it is hard enough to educate drivers not to overtake you and then immediately turn off onto a side-road (to the left on drive-to-the-left places or to the right on drive-on-the -right nations). Think how much harder it would be to require a driver to look ahead past the intersection and avoid turning until you had passed. Similarly, drivers entering from a side road into the flow of traffic would have to look both ways to avoid T-boning you. Hideously dangerous...
    – Penguino
    Commented Oct 9, 2016 at 23:45
  • The kinetic energy of the crash is also (65/25)^2 times more, making it much more injury and fatality prone. Commented Mar 7, 2021 at 14:40

Well, regarding the question asked: "why is it safer etc." let's go:

  1. (already mentioned) The closing speed between a car coming from behind is much slower. He has more time to see you before overtaking, and if you need to cross, you can signal your turn, so he can slow down for you to pass;
  2. By the same reasons, you can flow with traffic, take the lane, merge in and out, overtake, etc. only when riding with the flow;
  3. Pedestrians always look up the street for oncoming cars. If you ride the opposite way, there will be lots of pedestrians literally jumping in front of you;
  4. At night, there is a convention of bright white light front, not-so-bright red lights rear. If you ride against the flow, you obfuscate drivers and they obfuscate you with the lights' flares;
  5. (already mentioned) Bicycles are vehicles, so the direction of a street is, by definition, the same for motorized vehicles and bicycles.
  6. The air displacement effect on the balance of bike riders, and also on indirect "drafting", has a much greater negative effect if the biker rides against the main flow.

Actually, this whole discussion is pointless, but I think these are the most important reasons. Also, the very proposal of bikes riding that way BECAUSE a cyclist was hit by an automobile is the most cruel and typical exemple of "Ignoring the Bull". Have any of the people approaching this problem in your town considered to put the responsability in such accidents on the drivers?

Hope that helps, and good luck!

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    I agree, and the general agreement with most people is "why the heck would you do that." As I said in the question, "Explanations of why are welcome too, but please include some references or data." I know the reasons, I want some statistics to back up all of the logical explanations. Something to point at and say, "see, 200 people got in accidents going the wrong way, while only 100 got in accidents going the right way."
    – nhinkle
    Commented Apr 16, 2012 at 1:48
  • Bike accident stats in general are very scarce, and stats in this case would be even scarcer. In order to compare stats for wrong vs right way you'd have to have both the stats for the actual number of accidents (not available) and also the % of riders going the wrong way vs the right way (not even conceivable). (You could always write to League of American Bicyclists and ask for any info they might have, but I'm sure there's nothing of any substance published.) Commented Apr 16, 2012 at 1:59
  • @nhinkle I see only argumentation might not be enought. Perhaps following DanielRHicks' suggestion to write to the League (or some other big bike-advocacy institution) might be the right way to do it. Commented Apr 16, 2012 at 2:13
  • As anecdotal evidence supporting point 3, here in Barcelona two-way cycle lanes had been implanted in streets that were and still are one-way for cars. It's quite safe for cyclist because cycle lane is segregated, but it has lead to accidents with pedestrians who didn't expect a bicycle coming from a different direction than the other vehicles - even with cyclist being allowed to do so and the bicycle lane properly marked. Where it is not allowed it would be even more unexpected.
    – Pere
    Commented Oct 10, 2016 at 10:08

I believe there is an important point that hasn't been mentioned and it applies to driving too. It's always safest to do what is expected. People expect traffic to be going a certain direction. If a car is preparing to make a right turn onto a road, they are rarely going to check to see if there is any traffic coming from the right. I think a bike going against traffic is just as unexpected as seeing a car going against traffic. When everyone is following the rules, everyone knows what to expect.

Clearly we could change the rules to have cyclists ride against traffic, and eventually that could be what's expected. But I think that would just make the rules more complex, and simpler is better. The more overlapping rules cyclists and automobiles have, the better.

Of course accidents still happen (I know because currently recovering from a broken wrist from an oncoming car turning left in front of me on my bicycle), but all we can do is try to create the rules such that accidents are less likely to happen. I think the evidence provided by some other other answers shows that one is statistically more likely to be in an accident when going against traffic. I believe the reason for that is the one I've stated above.


The issue is actually quite complex. Some "wrong-way" routes can be quite safe if well-designed, marked, and implemented. Much of the data and research in this area is not published in English because "contresens pistes cyclable" or "unechte Einbahnstraßen" have been implemented in several European cities in France, Belgium, Germany, the Netherlands, and Switzerland, and in Japan. A previous bicycles.stackexchange answer referred to these bikeways here. In general, these "counter-direction" bikeways are in dense urban areas with many narrow one-way streets and restricted speed limits (usually, 30 to 40 km/h, or around 20 to 25 mph). A 200 page report from the Institut Federatif de Recherche sur Les Economies et Les Societes Indutrielles (one of the French research institutes) of the experiences in 5 French cities can be found here (in French) and a short PowerPoint presentation by the lead author of that study can be found here (again, in French). No accidents were observed on contresens bikeways in the study area during the period from 2002-6. A two-page illustrated brochure advocating the expansion of contresens urban pistes can be found here. In addition, a study of every bicycle fatality in Paris in 2005 had shown that the single largest cause of death was being right-hooked at intersections, and contresens bikeways completely eliminate this danger.

Having said all that, riding against traffic in unregulated, unsigned roads in the US appears to result in higher accident rates, as can be seen in the NHTSA/FARS data. The one-way roads that have been selected for two-way bike conversion in Europe are urban, speed-limited, and well-marked.

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    While this makes some great points, the question is about cyclists riding against traffic without appropriate cycling infrastructure. A question on this topic would be great, though - or perhaps a post on the site blog! Commented Apr 17, 2012 at 3:42
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    Oh, I'm pretty happy with what I wrote. The original question did not make any mention of presence or absence of cycling infrastructure, I linked to a report from a governmental research institute that discusses the exact reasons and conditions under which riding against traffic is a safe activity, I mentioned the NHTSA/FARS data in other situations, and I showed that the real world is actually quite complex. I'm willing to take downvotes on this.
    – R. Chung
    Commented Apr 17, 2012 at 5:25
  • Okay, fair enough. Commented Apr 17, 2012 at 5:27

According to Safety Camera, Hit someone at 40mph and there's an 80% chance they'll die, hit them at 30mph and there's an 80% chance they'll live. See the previous answers regarding closing speed of riding a bike into oncoming traffic.

This statistic is widely cited as the reason the posted speed limit in NYC is 30mph.

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    It would probably be best to lower the speed limit to 20 mph, then, so that people actually drive the safer speed of 30. :)
    – jscs
    Commented Apr 17, 2012 at 23:25

Bicycle is a vehicle going at significant speed. A cyclist is not a pedestrian. Pedestrians can quickly jump to the side away from the road while a cyclist would crash if doing that.

Pedestrians should face oncoming traffic if walking on road without sidewalks, since this allows quickly jumping away from the road should the pedestrian encounter a dangerous situation. A pedestrian walks maybe at 5 km/h, so on a road with 60 km/h traffic the choice is between 65 km/h delta and ability to quickly jump to side and 55 km/h delta with no such ability. Since kinetic energy is relative to the square of the speed, the difference is only about 40% more kinetic energy when delta is 65 km/h compared to when delta is 55 km/h.

A cyclist on the other hand goes at 25 km/h. If cars go at 60 km/h, the choice is between 35 km/h delta and 85 km/h delta. This is 490% more kinetic energy or in other words 5.9 times the kinetic energy if the delta is 85 km/h as opposed to delta being 35 km/h.

So if cycling on the side of the road, the cyclist should definitely go with traffic rather than against the traffic. What about dedicated cycling facilities, then? They should also be on both sides of the road so that the cyclist can go with traffic.

There are the following two dangers when riding against the traffic on dedicated cycling facilities.

  1. A cyclist and car driver are going to the same direction, with cyclist on the wrong side of the road. (I assume right-sided traffic here). Car driver decides to turn to left, signaling well in time, but there is oncoming car traffic so the car driver must wait. There is a very short break in the traffic. The car driver decides to quickly utilize that short break, and goes fast to left, trying hard to not collide with oncoming traffic. But oops! The car driver didn't know that a cyclist is arriving since the cyclist arrived from behind, not in front of the car. The car hits the cyclist and the cyclist crashes. If the cyclist had ridden on the correct side of the road, this would have never happened since the cyclist would arrive from front of the car.

  2. Cyclist is going to the wrong direction (wrong side of road). (I assume right-sided traffic here). Car driver approaches an intersection from the side, on a side road, and turns right. Since car driver turns right, the car driver must yield to traffic only from the left side (assuming a non-equal intersection here). However, the car driver didn't take into account there are cyclists going to wrong direction. The car hits the cyclist and the cyclist crashes. If the cyclist had ridden on the correct side of the road, it would have arrived to the intersection from the left side of the car, and the car would have properly yielded.

So, dedicated cycling facilities, if they have intersection with car traffic, should always exist on both sides of the road and the cyclist should ride in the direction of the traffic, rather than against the traffic.


Can a distinction be made between highway/rural riding and city riding? I have little experience in large city riding, but I grew up in the sparsely populated Upper Peninsula of Michigan, and find it rather 'common sense' to ride against traffic on two lane highways with shoulders.

  1. When traffic is whizzing past you at 55-70 MPH, it's very unnerving to not see them until they've already passed you, and startling when the wind attempts to blow you over with little warning.

  2. Traffic that attempts to 'pull over' would be coming right into your ass end, and you'd have no way of knowing without mirrors. I've been nearly hit twice like this before I switched.

  3. By being able to see the car and their position, it is easy to tell if they are drunk/texting/swerving (which is rather common) before they get near you, and quick to turn into the gravel / down the embankment to avoid them.

  4. As far as the 'additive speed' argument, you're screwed anyway at highway speeds. Even if you're riding at 20 MPH, most the traffic is ~65 MPH - so 45 MPH blind and oblivious or 85 MPH with a chance to dodge or bail off your bike

  5. Without a mirror, an attentive and responsible bicyclist could get hit by an incompetent / pulling over driver riding 'with' the grain. However, in an 'against' scenario, both drivers have the ability to avoid the collision, and both would have to be not paying attention for a collision to occur.

If you're confining this to city/urban riding only, that's fair - I just wanted to give some rationale behind the opposing view in certain situations (sorry I don't have any statistics). However, the statistics I see and safety guidelines seem to be from a densely populated/urban point of view.

  • The chart above was taken from data in the city limits of Palo Alto, CA for example.
    – Ehryk
    Commented Apr 16, 2012 at 17:03
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    Since the rules of the road are the same on both urban and rural roads, I would suggest that the acutal risk factors are quite similar. Having ridden the U.P. and Northern Wisconsin, I would concede that the risk-per-mile is less no matter which way you ride. This is only because there are fewer discrete encounters between motorist and cyclist. You can get away with riding against traffic for a lot longer, in rural areas than in urban because there are fewer chances to get whacked. That doesn't make the practice safer. All cyclists benefit from consistency among riders' behavior.
    – DC_CARR
    Commented Apr 16, 2012 at 19:28
  • I do quite a lot of rural riding and still find "with" better than "against", if only from the standpoint of familiarity. Granted, when there is a good, reliable shoulder it's not so critical, but rural roads have tendency to have "disappearing shouldlers", etc. (Of course, I also ride with a helmet mirror.) Commented Apr 16, 2012 at 20:07
  • But there are 'common sense' reasons for the opposing case as well. I'm for statistical backing on this issue, but it seemed such a one-sided consensus in here. I would argue that riding with traffic on highways without a mirror gives 100% control to the vehicle and 0% to the biker, where against traffic is perhaps 50% control - you have to have both drivers neglectful/not paying attention for a collision.
    – Ehryk
    Commented Apr 16, 2012 at 21:07
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    When I did a lot of cross-country touring in my foolish youth, we always invested in good quality rear-view mirrors to deal with the unexpected overtaking vehicle problem. After a few days experience and one unexpected logging truck, I was completely sold and would no more ride without a mirror than without a helmet.
    – RBerteig
    Commented Apr 16, 2012 at 22:59

An additional point that hasn't been mentioned is that normally the road infrastructure is not suitable for "against the flow" cycling. It may not matter much on straight country roads, but junctions are essentially always designed asymetrically. For example:

  • Junctions don't have a stop line or designated waiting space on the "wrong" side, cars turning into the junction arm where you are waiting will face you head on.

  • You don't get any slip roads and filter lanes for turning into side roads.

  • Traffic lights: If you're on the "wrong" side of the road, which traffic lights apply to you? The ones in your direction, or the ones in the opposite direction for "your" lane? You may not even be able to see the traffic lights. This gets really difficult in a complicated junction with different filter lights for different directions.

Exceptions are where the infrastructure is explicitly designed for that, for example a protected two-way bike lane with its own traffic lights etc.


Some diagrams and thoughts on wrong-way-riding: Go with the Flow

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    We prefer the main points of the content to be included in the answer... that way if the remote web site goes away, future readers will know what you said rather than facing a lonely 404 page.
    – Criggie
    Commented Oct 7, 2016 at 8:08
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    Welcome to Bicycles SE. We prefer answers on this site to be self-contained. That way, the answer is still valid if the link dies. Please summarize what information is contained in the link within the body of your answer. Otherwise, it is likely to be downvoted, flagged for moderator intervention, and possibly deleted.
    – jimchristie
    Commented Oct 7, 2016 at 17:12

It seems clear to me that beneath the question of whether one should bike in the same direction that traffic is going, or facing oncoming cars, lies another more important issue: Are bicycles of a similar class or group as other vehicles, or are they different? If bikes are considered to be a similar class of vehicles as cars, then they should all follow the same rules - including moving in the same direction. If one argues that cyclists should face oncoming traffic, then you are making the assumption that they are different (that is, that they are not an equal type of transportation vehicle, or even that they are toys).

In the interest of cyclists' right to share the road, clearly one should go in the same direction as traffic - to follow the same rules as all of the other vehicles which make use of the roads.

  • Actually, this is not the question. Regardless of how you legally classify bicycles, it's safer to cycle in the same direction as motor vehicle traffic in most circumstances. It does follow from this that bicycles should be regarded essentially the same as other vehicles, but the reason is safety (and other expediencies), not because of some primordial "right". Commented Jun 29, 2014 at 3:59
  • I'm making the argument that if bikes are the same as other vehicles, then they need to follow the same rules (which they do). It is safer if everyone follows the same rules on the road. What if they decided that it was better for trucks to go one direction and cars another?
    – Jason
    Commented Jun 29, 2014 at 4:01
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    While this is valid and tangentially relevant commentary, it doesn't answer my question at all. I'm asking why it's safer to ride with traffic, not what the societal implications are of which side you bike on.
    – nhinkle
    Commented Jun 29, 2014 at 4:15
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    @nhinkle I'm arguing that it would be safer if bikes were treated as a similar class of transport as cars (i.e. a "real" mode of transportation and not toys), thus riding in the same direction would be safer.
    – Jason
    Commented Jun 29, 2014 at 4:16
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    @Jason I understand, but that misses the point. You're addressing a broader question of "is it safer to treat bikes like cars or like pedestrians," not my question of whether it is actually safer or not specifically to bike with or against traffic.
    – nhinkle
    Commented Jun 29, 2014 at 4:26

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