This is an excerpt from Smart Cycling by League of American Bicyclists.
Approach intersections in the proper position. Vehicles turning right are closest to the curb, those turning left are near the centerline, and straight-through drivers are between these positions. Always travel in the right-most lane that leads to your destination. In single-destination lanes (or a two-lane street), ride on the right-hand side of the lane, except when stopping at a light when you plan to proceed straight through or when preparing for a left-hand turn.
Stopping at a Light
As you approach the intersection at a red light, give yourself plenty of time to scan behind you and look at the driver behind you, then signal, indicating that you are taking the lane. If the driver fails to yield, you can wait and simply stop behind the vehicle instead.
If you’re turning right, stay toward the right of the lane to indicate to the motorists behind you that you plan to turn at the light. However, if you plan to move straight through the intersection, position yourself in the middle of the lane. The danger of being to the right side when you are proceeding straight through is that motorists will pass and cut you off by turning right around you. If you position yourself in the center of the lane—by waiting behind the other waiting vehicles or standing astride your bike in the middle of the lane at the light—you’ll let cars know you’re proceeding straight, and you’ll be more visible. As the light changes, you can gradually move over when it’s safe to do so (check for parked cars on the right) and allow the other vehicles to pass you.
Left turns can be taken as a pedestrian would, by dismounting on the right side of the road and walking the bike across at controlled intersections. They can also be done more smoothly and swiftly by turning like a vehicle in traffic. Execute these turns only where you feel comfortable and after having practiced in low-traffic situations.
When preparing for a left-hand turn, you must move from the right lane to the right side of the left-turn lane farthest to the right. To get there, scan over your left shoulder, signal your move, and move twice per lane. In heavy traffic, you may be negotiating with drivers who want to pass. Make it clear what you are doing, remember you have the right to make a left turn from the same lane from which the cars are turning, and make sure you’re visible to drivers. On a two-lane street with no dedicated left-turn lane, you will simply move to the left side of the traffic lane moving in your direction, signal your turn, and yield to oncoming
To turn left on multiple-lane streets, you will have to cross over into the left lane or dedicated left-turn lane. If you are stopped for a light in this lane, position yourself according to the size of the lane. If it’s wide enough to share with a car, you can stay to the right of the lane. If it’s too narrow for both you and a car to comfortably share, take the lane. As a cyclist, you should be in the same lane you would be in if you were driving a car. Your position in the lane is an effective signal to other drivers to let them know which way you are going (figure 3.5). If there are double left-turn lanes, stay in the right-most one.
When executing the left turn, arc smoothly through to arrive at the right-hand side of the lane going in your direction. If you’re moving at the speed of traffic, take and hold the lane through the turn. Check for cars turning right on red that might be entering the same lane as you. You should yield to them.
Riding in Bike Lanes
On a roadway with bike lanes, you should treat the bike lane as an extra lane for cyclists only (that is, a lane that cars are not meant to use) and follow the rule of riding in the right-most lane that goes to your destination (figure 3.6). If the bike lane has debris or parked cars or is otherwise hazardous, you are not legally obliged to use it.
Never make a left-hand turn directly from a bike lane unless it is one specifically designed for bikes turning left. To make a left-hand turn at an upcoming intersection, you will need to get to the center of the street or regular left-turn lane by making your two lateral moves per lane. You must begin the process of changing lanes well before the turn.
Bike lanes provide many benefits for cyclists. Generally, because bike lanes are dedicated for cyclists, cyclists have elevated rights when traveling in them. For example, autos are not allowed to park in or impede the flow of a bicyclist in a bike lane. Bicyclists in a bike lane are also generally allowed to pass cars on the right, when they normally cannot do this. However, even though a cyclist has the right of way when going straight through an intersection, riders must be aware of right-turning vehicles that could cut them off. In a no-bike-lane situation, the auto has the right of way because bikers cannot pass a car on the right. In the bike lane, cyclists may have the right of way but should still be cautious; they will always lose in the event of a collision.
Well-placed and well-designed bike lanes are safe and fun to use. Bike lanes and other bicycle-friendly infrastructures have been shown to increase bicycling use, and with increased use and visibility, bicycling becomes safer and more visible to motorists.
However, bike lanes may also be poorly placed and designed. Cyclists should watch out for these situations and consider leaving the bike lane if it is in an awkward location. Sometimes bike lanes are on busy streets, and there may be a safer, more enjoyable route to your destination. In addition, bike lanes may have debris and other problems that might lead you to edge out of it or ride in the traffic lane. Ultimately, you should choose how you use or don’t use bike lanes, so remember to follow your instincts and the traffic principles.
Read more about Smart Cycling by League of American Bicyclists.