The Texas Transportation Institute’s annual Urban Mobility Report provides summary data for each urban area on operations strategy measures, estimating each one’s contribution toward reducing the travel time index.161 Four basic measures are reported, two for expressways and two for arterials. The expressway measures quantify the extent of ramp metering and the percentage of the system under active incident management efforts. The most recent expressway data for the Los Angeles region is shown in Table 37.
Table 37: Expressway Operations Management for the Los Angeles Urbanized Area
Operations Strategy 2011 2010 2009 2008
Ramp Metering
Percent miles of roadway 100% 99% 99% 100%
Annual delay reduction, (thousands of hours) 20,316 20,155 19,904 17,944 Freeway Incident Management
a) Cameras
Percent miles of roadway 71% 71% 70% 71%
b) Service patrols
Percent miles of roadway 95% 94% 94% 95%
Annual delay reduction, (thousands of hours) 18,285 18,139 17,913 16,149 Source: 2012 Urban Mobility Report, Texas A&M Transportation Institute, Texas A&M University. The Los Angeles Urbanized Area covers portions of Los Angeles and Orange Counties.
At 100% of miles covered, virtually every on-ramp in the Los Angeles – Long Beach – Santa Ana area uses expressway metering, resulting in estimated annual delay reductions of over 18 million hours.162 However, in other portions of Southern California, the percent of miles covered is lower (59% in Riverside-San Bernardino, and virtually no application in Oxnard-Ventura). Additional investments could reduce delay further and build on the region’s current successes in this area. If Riverside/San Bernardino and
Lancaster/Palmdale implement comprehensive expressway ramp metering where needed, the region might save an additional 1.1 million hours of delay. Since ramp metering costs much less than significant lane additions, this under-used tool clearly represents “low- hanging fruit” in reducing Southern California’s congestion. While ramp space can be an issue in some places, most of Riverside/San Bernardino’s and Lancaster/Palmdale’s expressways have enough “storage” space for vehicles in on-ramp queues.
Incident management has become a popular tool used to combat non-recurrent congestion in large metropolitan areas. Typical incidents include disabled vehicles, traffic crashes, spilled cargo or other debris in the road, road construction and non-emergency special
incident detection and verification, incident response and clearance, and site and area traffic management. One of the more obvious examples of the deployment of this strategy is the variable message signs over expressways throughout the region alerting travelers to delays and traffic accidents.
Two key elements include equipping the expressways with cameras so that incidents can be identified quickly and appropriate units dispatched, and creating and operating
expressway service patrols that can respond rapidly to minor incidents (breakdowns and fender-benders). On the former, Los Angeles is ahead of the pack, with 71% of
expressway-miles equipped with traffic surveillance cameras as of 2011, compared to an average of 52% for other large metropolitan areas.163 Riverside-San Bernardino does even better at 77% and Oxnard-Ventura at 24%. However, those percentages have held steady for the past four years. Each region should try to cover the remaining expressways within the next five years.
Los Angeles also has expressway service patrols in place, covering 95% of expressway- miles. Riverside-San Bernardino covers 78%. The patrols’ duties include detecting expressway incidents by patrolling metro expressways and quickly responding to and removing incidents (pushing disabled vehicles using push bumpers and removing debris) from the traffic lanes. They are also responsible for providing traffic control and scene security at crashes, assisting first responders with first aid at crash scenes and assisting motorists with emergency vehicle repairs. Service patrols also clear stalled vehicles and debris in the roadway. The congestion from these incidents is responsible for causing about 15% of all expressway crashes, known as “secondary crashes.”164 Every minute a highway lane is blocked can cause four to five minutes of additional delay, so it is critical to clear the roads as quickly as possible.165
Several states have analyzed the congestion created by incidents and the advantages of better incident management systems. The Washington State DOT estimates that the throughput on a six-lane expressway (three per direction) can be cut 20% by a car out of gas on the shoulder, 50% by a disabled car blocking one lane, and 85% by an accident blocking two lanes.166 Rapid response and rapid clearance of such incidents can
significantly reduce the duration of such congestion, allowing the expressway’s capacity to be reclaimed. The Bay Area Toll Authority estimates a benefit/cost ratio for such projects as 8:1.167 Such projects typically involve advanced video systems to quickly spot incidents, dispatch centers to send appropriate response crews and expressway service patrols to quickly deal with minor incidents.
Table 38: Expressway Service Patrol Data
Urbanized Area Annual Cost ($ million) Miles Covered # Vehicles Benefit/Cost*
Los Angeles, CA $23.1 411 146 tow trucks 15:1
San Francisco Bay Area, CA $6.0 362 60 tow trucks 11:1
Chicago, IL $5.5 80 35 tow trucks 17:1
San Diego, CA $2.4 203 26 tow trucks 7:1
Houston, TX $1.4 190 18 vans 6.6:1 to 23:1
Denver, CO $1.3 60 12 tow trucks 20:1 to 23:1
Minneapolis/St.Paul, MN $1.0 220 10 pickup trucks 15.8:1 Source: Regional Transportation Management Center
*The benefit/cost calculations are not directly comparable due to the differing assumptions and methods used between agencies. MnDOT’s benefit/cost ratio was calculated more conservatively than other metro areas.