A Discussion on the Current MUTCD Standards on Traffic Control Signals for Freeway Entrance Ramps

Abstract

ABSTRACT In Section 4I.02 of the newly published Manual on Uniform Traffic Control Devices (MUTCD), standards were specified for the placement of signal heads for traffic control signals at freeway entrance ramps, or ramp meters. For simultaneous operations, i.e. when ramp control signals are operated such that green signal indications are always displayed simultaneously to all of the lanes on the ramp, a minimum of two signal faces per ramp shall face entering traffic. For staggered operations, i.e. the ramp control signal are operated such that green signal indications are not always displayed simultaneously to all of the lanes on the ramp, one signal face shall be provided over the approximate center of each separately-controlled lane. Based on a nation-wide survey, it was realized that the two standards did not fully reflect the state-of-the-practice with respect to ramp metering operations. Due to the lack of significant conflicting movements at ramp meters, for any on-ramp lane, a minimum of one overhead mounted, or one upper and one lower roadside-mounted signal face is sufficient to control the metering operations. The minimum necessary number of signal faces changes according to the total number of lanes, how the signal faces are mounted (overhead or roadside mounting), and how the meters are operated (simultaneous or staggered). Suggestions are made to revise the two standards to better reflect the current nation-wide practices, and better consider the specific operational needs for ramp meters.