Why is it safer to bike with traffic, instead of facing oncoming cars?

Question

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.

Answer 1

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 Observed	Accidents Reported	Risk	Bicyclists Observed	Accidents Reported	Risk	Risk Ratio	p
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.

Answer 2

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.

Answer 3

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!

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

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.

Answer 8

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.

Answer 9

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.

Answer 10

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

Answer 11

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.