Editing Ramp meter (section)

=== Mainline metering ===
A '''mainline meter''' throttles traffic flow from one segment of a highway to the next by directly metering the highway's traffic. Such a scheme is typically implemented in specialized situations such as bridges and tunnels. A mainline meter was installed at the [[San Francisco–Oakland Bay Bridge]] toll plaza in the early 1970s. Similar mainline meters have also been installed downstream from the toll plazas at two other San Francisco Bay crossings, the [[San Mateo Bridge]] and the [[Dumbarton Bridge (California)|Dumbarton Bridge]]. However, these mainline meters have not yet been activated (as of September 2006).{{update inline|date=December 2020}} A mainline meter also exists on [[California State Route 125]] southbound at its junction with [[Interstate 8 (California)|Interstate 8]] in [[La Mesa, California]].