Knowledge Resources

Dynamic Turn Restrictions

Bellevue, Washington implemented a variable right turn restriction on the eastbound right turn movement at NE 8th Street and Bellevue Way using illuminated blank-out signs. The eastbound movement here is the main exit route from a shopping mall that occupies three quadrants of the intersection. High pedestrian traffic, essentially blocking eastbound right turning vehicles, can reduce eastbound capacity by 50 percent. Actuation of the dynamic restriction is based on occupancy data from an upstream detector. A blank-out sign at the intersection illuminates the traditional R3-1 sign. There is also an advance sign over the curb lane that can display two states: a through/right arrow and a through arrow only. Timers were implemented to ensure the turn restriction stays in the same state for at least 10 minutes. There is also a manual switch so police officers can manually turn the restriction on or off.

Lessons Learned

Bellevue respondents indicated that the success of the turn restriction strategy depends on three things:

1. Drivers need to see a need for the restriction
2. The presence of reasonable alternative routes
3. Periodic police enforcement.

Bellevue respondents also pointed out that many ticketed drivers say they never saw the signs, so visual clutter may be a concern. Keep logs of when the sign is operational. During the first year many ticketed drivers requested operation logs because they said the sign was permissive when they received the ticket.