The garbage truck and driver who killed Alice Swanson two years ago was making an improper turn, but most drivers would make the same mistake. The correct procedure is for drivers to merge into the bicycle lane before the intersection, then turn from that lane.
Why? Let’s say you’re driving in a motor vehicle on a road with two standard general-purpose lanes going in the same direction. You are in the left hand lane. We all know that if you want to turn right, you should first signal to change lanes, look right to make sure the other lane is clear, then move into that lane. Then, you turn from that lane.
Bicycle lanes are lanes too. They’re specifically “restricted lanes.” Many of them are narrow, but for the purposes of vehicle movements, proper driving procedure treats them as lanes like any other.
Therefore, if you want to turn right, when there is a bicycle lane on the right side of the road, you should signal right to change lanes, look to ensure there are no bicyclists in the lane, then move into the lane. You are then blocking the bike lane, so cyclists don’t pull up on the right. You can then signal again to turn right and make the turn.
How far ahead? According to the DC regulations, it should be anywhere within the block approaching the turn:
2203.3 Both the approach for a right turn and a right turn shall be made as close as practicable to the right-hand curb or edge or the roadway.
2220.2 ... [A]ny vehicle may enter a restricted right curb lane solely for the purposes of taking on or discharging passengers or to make a right turn where a right turn is not otherwise prohibited by any official traffic control device.
2220.3 Vehicles entering a Restricted Lane to make a right turn or to discharge or take on passengers shall be permitted to enter the Restricted Lane only within the same block as the right turn or passengers are to be taken on or discharged.
2220.4 Vehicles, other than those to which a lane is restricted, are prohibited from continuing through an intersection in a Restricted Lane.
Sometimes when I do this as a driver, cyclists will still try to squeeze between my car and the curb to go straight. This is incorrect and unsafe. If you are a cyclist riding in a bike lane and a car pulls into the lane with its right blinker on, you should wait behind the car until it makes its turn. Update: Or, you can merge into the adjacent general-purpose lane, assuming there’s room, and ride in that lane.
This DDOT/WABA PSA video about not cutting off cyclists shows the driver using the correct procedure, moving gradually into the bike lane with a fair amount of distance before the intersection.
Michael Perkins found a great animation from The Oregonian comparing California’s law, which matches DC’s, and Oregon’s, which is (or was, in 2007) different. Oregon required motor vehicles to stay in the general-purpose lane and turn across the bike lane when it’s safe. That lets cyclists overtake cars about to turn, which might be why some advocates opposed the change, but it’s more dangerous.
Unfortunately, as matthias noted, the Oregon procedure is what most drivers believe they are supposed to do. Now you know.