Passing Thoughts -- Bikes and Cars Sharing the Road

by Fred Oswald, Bicycling Safety Instructor

People with little experience riding in traffic are often upset and frightened by motor vehicles passing close and fast.  Ironically, beginners may unintentionally invite this close passing by "hugging the curb".  As an experienced cyclist, I rarely have this problem.  Instead, I occasionally see motorists passing *too far* away.  (At least on narrow, 2-lane roads.).  That's right; some people give too much room.  What's wrong with that?  Let's consider.

As a useful rule of thumb, motorists should allow at least 3 feet of clearance when passing a bike.  A bit more room is better -- say 5 or 6 feet [1].  This rule assumes good conditions:

  1. The cyclist is predictable and under control.  Some novices and especially children weave and wobble.  They are not predictable so allow extra room.
  2. The car is not going too fast.  If you are going more than 15 mph faster than the cyclist, then the minimum must be 5 feet.  Over 50-60 mph, you should allow even more space, especially if you drive a large truck, which makes a wind blast.
  3. The road is in reasonable condition.  If not, be wary that a beginner may swerve to avoid a hazard.
  4. The motorist is in good control of the car and can see that no wide vehicles are coming from ahead.

But what's wrong with giving lots of extra room even if it is not needed?  I often see drivers go completely into the next lane to pass -- over twice the clearance needed.  On a 2-lane road, this means they are driving on the wrong side as they pass.  Also, moving out so far takes much longer.  Some do this on a blind curve or even in the face of oncoming traffic.  These people foolishly risk a head-on collision.
Blind curve

Another error is made by timid drivers, not passing when they could.  This means they hold up traffic unnecessarily.  But more common are aggressive drivers who won't wait even two seconds for safe conditions.  They force their way by on curves or in other places where they cannot see.

Experienced cyclists try to discourage this dangerous behavior by "controlling the lane" and sometimes holding out the left hand (as shown in the photo at right) until it is safe to pass.  Law enforcement officers can stop unsafe passing by riding in plain clothes and issuing citations to perpetrators.  Any such "sting" must be publicized to be effective.

Where to Ride

Cyclists need to learn the best lane position for riding on the road.  Where conditions, including lane width and other factors, allow safe and reasonable passing within the lane, then ride just far enough right to facilitate passing (about 3' from the travel lane).  If not, then say far enough to the left to show passing drivers that they must go at least partly into the next lane to get by.

The right tire track is often a good place to be when the lane is narrow.  Consider this your normal riding position on a narrow-lane road.  But on a high-speed road, you may need to ride further left -- perhaps the left tire track -- so overtaking drivers can recognize that the lane is occupied early enough.

Notice in the photo at right, the lanes are narrow but passing motorists are giving ample room because the cyclist is near the middle of the lane.  This position complies with traffic laws that require riding as near to the right side of the roadway as practicable (practice+able) [2].  Understand that, it is not practicable to encourage dangerous passing.

Riding near the middle of the lane means controlling the lane.  This deters many motorists mistakes and makes you more visible.  It also takes advantage of the principle "Take more space to get more space."  If you ride in the gutter or squeeze close to parked cars, motorists take that as a cue for them to squeeze past!

Help traffic pass when safe & reasonable.  How to do this?  The most difficult passing situation is a narrow, 2-lane road with heavy traffic.  If following drivers are able to find a gap in the oncoming traffic stream to pass, let them do so.  However, if they are not able to pass, then look ahead to find a safe spot where you can help them, considering the road condition, oncoming traffic, etc.

When you find a safe place, then move to a lane-sharing position, close to the edge of the road.  Because any traffic backed up behind you has slowed to your speed, you do not need as much clearance as you would for faster traffic.  Once the "platoon" has passed, look back first, then move back to your normal position [3], near the middle of the lane (or perhaps the right tire track).

Very, very rarely you may not be able to let traffic pass safely as described above.  In such situations however, other vehicles will probably have tied-up traffic ahead.  Then, even if you would let them pass, they cannot go much faster.  But for the exceptional case where you really are delaying people, find a safe place, pull off the road, let the backed-up traffic pass, then resume your journey.  As a regular commuting cyclist, I have never had to do this.  I have always found either I am able to let traffic get by reasonably soon or traffic is so congested I am able to keep up.

Delaying Traffic:  Perception vs Reality

Many non-cyclists believe that bicycles on the road "get in the way" and delay "real traffic".  Much if this is due to the attitude that cyclists are just playing in the road and that they do not deserve to use roadway space.  There is also the attitude that motorists have the right to drive at the speed limit, if not faster.

The reality is that ALL vehicles delay traffic.  This is a consequence of the law of nature that two objects cannot occupy the same space at the same time.  While bikes sometimes delay traffic, so do cars.  Think about this next time you are waiting for a car to make a left turn ahead of you.  If that were a bike, you would probably have room to be on your way.

Likewise, a courteous cyclist stopped at a traffic light will move up and to the left to allow following motorists to turn right on red, if it is safe and legal.

The actual delay to traffic from a bicycle is almost always trivial.  Most traffic is able to pass with no impact other than slowing a bit and perhaps changing lanes.  Occasionally, a passing driver must wait a few seconds in order to fit a gap for safe passing.  Very rarely is the wait as much as 30 seconds.

Remember, the passing driver needs only to slow to the speed of the bicycle.  Typically, the bicycle is traveling at half the speed limit, so the delay is half what it seems.  Then after passing, the driver can go faster in the open space ahead of the bicycle.  Most soon catch up to their earlier place in the traffic queue.  This means the real delay is usually zero.

I often see someone pass me in a huff, and then shortly the brake lights come on as that driver catches up to other traffic.  The motorist will perceive that I caused a delay.  The reality is there was no delay.  The presence of my bicycle simply redistributed the delays already present due to the other traffic [4].

Both cyclists and motorists must use courtesy on the roads.  Better driving by all improves safety and allows efficient traffic flow.


[1] For more information about coexistence between motorists and cyclists, see the article "Advice to a Motorist:  How to Pass a Cyclist" on Ken Keifer's extensive web site:  For more bicycle driving information, see the LAB Reform Education Section.

[2] The Uniform Vehicle Code, 11-1205(a) Position on roadway says this:
Any person operating a bicycle or a moped upon a roadway at less than the normal speed of traffic at the time and place and under the conditions then existing shall ride as close as practicable to the right-hand curb or edge of the roadway except under any of the following situations: ...  [The exceptions spell out some, but not all, of the conditions where riding close to the edge of the road is not safe: passing, preparing for left turn, avoiding hazards (including where the lane is too narrow for sharing) and where there is a right turn lane.]

[3] The "normal position" vs the "secondary position" is discussed in Cyclecraft by John Franklin. This British book is now available in a North American edition.

[4] For a through discussion of the delay issue, see chapter 8, "The Effect of Cyclists on Traffic" in the book Bicycle Transportation, MIT Press, 1994.

© Copyright 2004-2017 Fred Oswald.  May be copied with attribution.
The author is a certified Biycling Safety Instructor and a Professional Engineer in Ohio.
Apr 2017