Originally Posted by
CommuterRun
I'm not a judge, but to me cyclists riding two abreast do not impede the flow of traffic if the lane is too narrow for a bicycle and a motor vehicle to safely share. In other words, if the lane is narrow enough that the cyclist should be in a road position that a motorist would have to change lanes to pass, then it doesn't matter if it's a single cyclist, or two side by side.
However, in a lane wide enough to safely share that would not apply. On any road with more than two lanes, the motorist can pass in another same direction lane.
Here's Delaware's take on impeding traffic:
Originally Posted by DE Traffic Code
§ 4125. Turning off roadway by slow-moving vehicle.
On a 2-lane highway where passing is unsafe because of traffic in the opposite direction or other conditions, a slow-moving vehicle, behind which 5 or more vehicles are formed in line, shall turn off the roadway wherever sufficient area for a safe turnout exists, in order to permit the vehicles following to proceed. As used in this section, a slow-moving vehicle is one which is proceeding at a rate of speed less than the normal flow of traffic at the particular time and place. (60 Del. Laws, c. 701, § 24.)
This is a pretty standard law as it's used in other US states as well.
Notice that it only applies on a two lane highway (one lane each direction) and that you only need to pull over when a safe turnout exists assuming that the faster traffic cannot pass using the other traffic lane. I've only had to do this a few times while cycling in the past 15,000 miles or so. It takes a pretty busy road or a very twisty road with a decent amount of traffic before this situation occurs. FWIW, if I'm going 20 in a 25, I couldn't care less how much traffic is behind me. 20 in a 25 is plenty normal for me
When I'm under the speed limit by 15-20mph is where I start considering myself "slow."