Traffic signals create gaps in traffic flow, allowing bicyclists, pedestrians, and motorists to access or cross the street. Signals are particularly important for crossing higher speed roads, multi-lane roads or highly congested intersections. National warrants from the Manual on Uniform Traffic Control Devices (MUTCD) are typically used for new signal installation.¹ Part 9 of the MUTCD focuses on "Traffic Calming for Bicycle Facilities." Some states have their own supplement to the MUTCD.

In downtown areas, signals are often closely spaced, sometimes at every block. A problem for bicycles is that signals are timed to accommodate typical motor vehicle speeds and flows. The motor vehicle speeds can be significantly faster than bicycle speeds. In addition, the clearance interval for motor vehicles crossing a wide intersection may not be long enough to ensure safe clearance by bicycles.

Although little research is available, timed sequencing of signals may take bicycling into account. Some cities time their downtown urban traffic signals to account for speeds of 20 to 25 km/h (12 to 16 mph), which allows bicycles to easily ride with traffic.

In locations with high volumes of bicyclists, traffic signals for bicycles can be used. These have been popular in Europe and China for many years. The City of Davis, CA, where bicycling accounts for approximately 17 percent of the mode share, has effectively employed a bicycle traffic signal to reduce conflicts and crashes between bicycles and motor vehicles at a location with very high volumes of bicycles and pedestrians. The bicycle signal provides a separate phase for bicyclists and pedestrians, with motorists following after the intersection has cleared (see case study #39). "NO RIGHT TURN ON RED" signs are also used.