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Planning Guidance for the Installation and Use of Technology Devices for Transportation Operations and Maintenance

ENTERPRISE Transportation Pooled Fund Study

Ramp Meter Guideline 1 - Corridor-Wide Freeway Traffic Management

Purpose: To address the need for a ‘zone’ of Ramp Meters along a stretch of freeway (typically considered in 3-6 mile segments).

The planning guidelines for ramp meters are presented as one tool to assist agencies in selecting deployment locations, and are not a replacement for the planning or design process.  Also, prior to deploying a ramp meter  System, ensure the basic requirements of the MUTCD (2009 Edition Chapter 4I. Traffic Control Signals for Freeway Entrance Ramps) have been met at the location of concern.

Engineering judgment should be used to assess potential implications that may result from installation of ramp meter.  This planning guidance does not mandate the use of ramp meters.

 

1a. Control Factors. During the AM or PM Peak Period, the Zone in consideration has at least 30 minutes per commute day (measured in 5 minute increments) where the demand is equal to or exceeds 95% of the downstream capacity, according to the following equation?

MV + OR > (ER + MC) *.95

Where:

MV = Upstream Mainline Volume (in veh/5 min.)
OR = The sum of On-Ramp volumes of ramps within the zone (in veh/5 min.)
ER = The sum of Exit Ramp Volumes within the zone (in veh/5 min.)
MC = Downstream Mainline Capacity (in veh/5 min.)

OR

1b. Platoons from signalized intersections are recognized to adversely impact ALL on-ramps feeding the freeway segment under consideration. For example if hourly volume, based on maximum 30 second volume readings projected to hourly volumes, exceed 1100 vph. (regardless of overall hourly volume).

Note: Overall hourly volume entering from arterials may be relatively low (e.g. 700 vph. However, during periods when platoons arrive, if 30 second readings of volumes represent 1100 vph or greater, this factor is considered met.

AND

2. Safety Factors. There is one or multiple area(s) within the zone where crashes are understood to exceed the typical crash rate (at the ramp gore point or within 500 feet in either direction of the gore point) for the metropolitan area. (1)

AND

3. Functionality Factors. Volumes at ramps being considered for meters, within the zone, fall within the range of 240 – 900 vphpl during peak periods. (2)

References:

(1) Federal Highway Administration. 2003 Edition, Manual on Uniform Traffic Control Devices. 2003.
(2) Caltrans, Traffic Operations Program. Ramp Meter Design Manual. 2000.