South Dakota law says a rider can move from the right-hand curb or edge of roadway when the lane is substandard width.
South Dakota law defines a substandard width lane as a lane that is too narrow to safely share side by side with another vehicle.
The question at hand; what is “too narrow?”
Determining too narrow is more of an art than a science.
If the driver or rider is drunk, texting, sleeping, talking on the phone, or fighting with the kids in the back seat there’s not enough pavement in the world to make a lane wide enough to safely share side by side with that vehicle.
Speed plays a role too. It is much easier to share a lane side by side with a car going 20mph than a car going 80mph.
The ability of a rider to ride predictably straight also plays a role.
Let’s see if we can find an empirical width. In feet. Something we can put a tape measure to.
1. How many feet do you need to your right between you and the curb to feel like you’re riding safely?
2. How many feet wide are you?
3. How many feet do you need to your left between you and a passing car?
4. How many feet wide is a passing car?
Typically when these four numbers are added together you’ll get between 14’ and 18’. The bike safety experts I know will readily agree that a 14’ lane can usually easily be shared side by side with a car.
Fact: MOST South Dakota lanes are 10’ or 12’. So, which lanes are too narrow to safely share side by side by a bicycle and a car? MOST.
Here’s how I apply this to the way I ride.
I look ahead as far as I can see and pick the left most lane position that will afford me safe passage by any obstacles to my right. Most often it’s a parked car so leftward enough to safely pass if the car door opens while I’m riding by.
Any driver that sees me immediately realizes there is not enough space in the lane to pass me. Expectations are set.
When I become aware of a driver behind me I evaluate the situation. Can I safely move to the right to give the driver more space to pass? When can I safely move to the right to give the driver more space to pass?
When I can move right, I do move right.