Compare and contrast the different metering systems that are used in traffic signal ramp control indicating under what conditions you will use each.

Question

What will be an ideal response?

Answer 1

Ramp metering control systems can be divided into two general
categories: pre-timed and traffic response. The traffic response category can be
further divided into local traffic responsive and systemwide traffic responsive.
Pre-timed systems involve the use of traffic data only from a historical
perspective; therefore their operations cannot be altered in an automated real-time
environment and therefore do not require communication with a traffic
management center (TMC). In contrast, traffic response systems utilize current
traffic data as an input to their control algorithms. This category can therefore
respond to changing traffic conditions if traffic data being collected are made
available to the control algorithm. Local traffic responsive control is based only
on conditions immediately upstream and downstream of the ramp junction, while
systemwide traffic responsive systems allow ramp meter control to be based on a
corridor or systemwide optimization of traffic flow.
Pre-timed control would typically be used for an isolated location or in an
area without traffic monitoring or real-time data collection capabilities. Traffic
response control would require real-time data collection; local traffic responsive
control would typically be used for isolated locations or locations without
communications capabilities, while systemwide traffic responsive control would
typically be used in a system with many ramp meters along a corridor and the
ability to communicate with a TMC. In the event of a communications loss or
other failure of a system wide control algorithm, these systems can be
programmed to revert to a local traffic responsive control or to a pre-timed
algorithm