2.2 Freeway Management Systems

There are six major ITS functions that make up freeway management systems, as shown in Figure 2.2.1. Traffic surveillance systems use detectors and video equipment to support the most advanced freeway management applications. These sensors can also be used to monitor critical transportation infrastructure for security purposes. Traffic control measures on freeway entrance ramps, such as ramp meters, can use sensor data to optimize freeway travel speeds and ramp meter wait times. Lane management applications can promote the most effective use of available capacity on freeways and encourage the use of high-occupancy commute modes. Special event transportation management systems can help control the impact of congestion at stadiums or convention centers. In areas with frequent events, large changeable destination signs or other lane control equipment can be installed. In areas with occasional or one-time events, portable equipment can help smooth traffic flow. Advanced communications have improved the dissemination of information to the traveling public. Motorists are now able to receive relevant information on location-specific traffic conditions in a number of ways, including dynamic message signs (DMS), highway advisory radio (HAR), in-vehicle signing, or specialized information transmitted to individual vehicles. Other methods of providing traveler information, including those covering multiple modes or travel corridors, are discussed in Section 2.7–Traveler Information. Automated systems enforcing speed limits and aggressive driving laws can lead to safety benefits.

Table 2.2.1 provides information on the benefits and costs of freeway management systems. An assessment of the impact of these systems is indicated by using the symbols in the Impact Legend at the bottom of each page.

Table 2.2.1 – Benefits and Costs of Freeway Management Systems

Traffic Surveillance

Benefits
Supporting role, no benefits information.
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Detection subsystem Transportation Management Center subsystem	See Appendix A
(New) System Cost	The Florida Department of Transportation (FDOT), ITS Division, examined the design factors for closed-circuit television (CCTV) video camera sites and how the design and maintenance issues impact the life-cycle costs. FDOT reviewed studies on this subject and collected information from similar projects in other states. Pole height and effect on camera system performance, site placement and spacing, coverage area, environmental impacts, and use of camera-lowering devices are detailed in the report. The costs of several alternatives based on pole height and mounting with/without camera-lowering devices are compared in the report.[70]	Camera site, initial costs: $16,550–$27,550 Camera system, life cycle costs: $403,650–$835,000
(New) System Cost	The Utah DOT employs traffic monitoring stations at approximately 1/2 mile intervals along Salt Lake Valley freeways as part of the Utah Advanced Transportation Management System (ATMS). The in-pavement congestion sensors allow Commuter-Link operators to monitor traffic conditions. The sensors provide operators with information on traffic volume, speed, and congestion. Annual operational cost is based on power consumption (electricity).[3]	Congestion sensor cost: $2.1 million Annual maintenance cost: $42,000 Annual operational cost: $37,800
(New) System Cost	The Illinois Department of Transportation (IDOT) District 8 will be deploying ITS field devices in conjunction with several multimillion dollar construction projects. Technical and cost options were evaluated and presented to IDOT District 8 for a communication network connecting the ITS field devices to the transportation operations center. At the time of the study, a number of ITS devices were connected via leased telecommunication lines. IDOT desired to move away from the leased communication structure and associated recurring monthly costs. The major interstates in District 8 collectively encompass approximately 105 miles of centerline highway. The ITS devices that would be deployed along these interstates include CCTV cameras with pan/tilt/zoom, video detection stations, DMS, and HAR. Technical and non technical issues as well as initial and long-term costs were considered in the various communication alternatives. Initial capital cost, operations and maintenance (O&M) costs, and 15-year life-cycle costs are provided for four communication options.[71]	For the four options evaluated, capital costs range from $18.1 million to $26 million, and life cycle costs range from $43 million to $52.5 million

Ramp Control: Ramp Metering

Benefits
Goal Area	# of Studies	Impact	Example
(New) Safety	5	+	A survey of traffic management centers in eight cities found that ramp metering reduced the accident rate by 24–50%.[72]
Mobility	8	++	Two studies in Minneapolis-St. Paul, Minnesota, and one in Long Island, New York, place mainline speed increases on freeways with ramp metering between 8% and 26%.[73, 74, 75]
Capacity/ Throughput	3	++	The Minneapolis-St. Paul, Minnesota, shutdown study found that freeway volumes were 10% higher with ramp meters than they were during the shutdown.[73] A study in Glasgow, Scotland, found freeway volumes increased by 5% with ramp metering.[58]
Customer Satisfaction	3	++	Support for complete shutdown of the Minneapolis-St. Paul, Minnesota, ramp metering system dropped from 21% in 2000 to just 14% of survey respondents after implementation of a modified operating strategy in 2001.[73] Fifty-nine percent of survey respondents in Glasgow, Scotland, found ramp metering to be a helpful strategy.[58]
Energy/ Environment	1	?	A simulation study of the Minneapolis-St. Paul, Minnesota, system found 2–55% fuel savings for vehicles traveling along two modeled corridors under varying levels of travel demand.[74]
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Control subsystem		See Appendix A
(New) System Cost	The Utah DOT employs 24 freeway ramp meters as part of the Utah ATMS. Ramp metering consists of sensors and traffic signals at freeway entrances to control the number and frequency of vehicles entering the freeway. The capital cost of ramp metering is the full cost to implement, including the design, equipment, and installation.[3, 76]		Cost of ramp metering is the full cost to implement, including the design, equipment, and installation: $5,750,000 Annual maintenance cost: $13,800 Annual Operational cost: $8,280

Lane Management: Lane Control

Benefits
Goal Area	# of Studies	Impact	Example
Safety	1	?	Traffic surveillance, lane control signs, variable speed limits, and dynamic message signs in Amsterdam, the Netherlands, have led to a 23% decline in the accident rate.[65]
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Control subsystem Transportation Management Center subsystem		See Appendix A
System Cost	No data to report.

Lane Management: Variable Speed Limits

Benefits
Goal Area	# of Studies	Impact	Example
Safety	1	?	In England, variable speed limits supplemented with automated speed enforcement have reduced rear-end accidents on approaches to freeway queues by 25–30%.[65]
Capacity/ Throughput	1	?	Combined with automated speed limit enforcement, an English variable speed limit system has increased freeway capacity by 5–10%.[65]
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Control subsystem Roadside Detection subsystem Roadside Information subsystem		See Appendix A
System Cost	Washington State DOT (WSDOT) implemented Travel Aid, a variable speed limit system that changes as the weather does, along the Snoqualmie Pass (I-90) east of Seattle, Washington. Approximately 13 miles are operated as variable speed limit during the winter months. The system consists of radar detection, six environmental sensor stations (ESS), nine DMS, and radio and microwave transmission systems.[53, 77, 78]		Design and implementation cost: $5 million (1997)

Special Event Transportation Management

Benefits
No data to report.
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Information subsystem Parking Management subsystem	See Appendix A
System Cost	No data to report.

Information Dissemination: Dynamic Message Signs

Benefits
Goal Area	# of Studies	Impact	Example
Safety	1	?	A San Antonio, Texas, deployment of DMS, combined with an incident management program resulted in a 2.8% decrease in crashes.[10]
Mobility	14	+	A simulation study of the system deployed on the John C. Lodge freeway in Detroit, Michigan, estimated that HAR and DMS in combination with ramp metering may reduce vehicle delay by up to 22%.[79]
Customer Satisfaction	7	+	Mail-back questionnaires were sent to 428 drivers living near major freeways in Wisconsin to assess the impacts of posting travel time and traffic information on DMS throughout the state. A total of 221 questionnaires were returned and analyzed. The results indicated that 12% of respondents used the information more than five times per month to adjust travel routes during winter months, and 18% of respondents used the information more than five times per month to adjust travel routes during non-winter months.[2]
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Information subsystem Transportation Management Center subsystem		See Appendix A
(New) System Cost	The Utah DOT operates and maintains more than 69 permanently mounted variable message signs (VMS) on freeways and surface streets as part of the Utah Advanced Transportation Management System. Portable message signs are also used along roadsides where there is no permanent VMS. Annual operating cost for the VMS is based on power consumption (electricity).[3]		Cost of VMS: $15.25 million Annual VMS operating cost: $21,960

Information Dissemination: Highway Advisory Radio

Benefits
No data to report.
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Information subsystem Transportation Management Center subsystem	See Appendix A
(New) System Cost	Washington State Department of Transportation (WSDOT) installed a system in the rural and mountainous region of Spokane to collect and communicate weather and road conditions, border crossing status, and other information to commercial drivers, the motoring public, and WSDOT maintenance crews. As part of this system, two ESSs were installed at Sherman Pass and the town of Laurier, and two mobile HAR systems were installed near the town of Republic and at the town of Kettle Falls. Broadcasts warn motorists of road construction, incidents, dangerous driving conditions and restrictions, and border crossing conditions and closures.[20]	Two ESSs: $45,000 each HAR cost: $111,073 – Two mobile HAR: $52,000 – Signs, connectivity, clearing, and other associated costs: $59,073
System Cost	Washington State DOT deployed three HAR stations along the Blewett/Stevens Pass to provide weather and road condition information to travelers and maintenance crews. One portable and two fixed HAR stations were deployed. Annual O&M costs are based on prior experience to operate and maintain.[13]	Average cost of the HAR (including installation): $20,000 (2001) Annual O&M cost: $1,000 (2001)

Enforcement: Speed Enforcement

Benefits
Goal Area	# of Studies	Impact	Example
(New) Safety	10	++	A study of two years of crash data following deployment of speed cameras at study sites throughout Great Britain found a 35% reduction in the number of people killed or seriously injured at camera locations. There was a 14% decline in the number of personal injury accidents.[67]
Customer Satisfaction	3	+	Eighty-two percent of survey respondents in the Washington, D.C., area favored video technology used to enforce aggressive driving laws such as not speeding and not following too closely.[80]
Costs
Unit Costs Database	Roadside Telecommunications subsystem Roadside Detection subsystem		See Appendix A
(New) System Cost	In April 2000, a cost recovery system for speed and red-light cameras was introduced in eight pilot areas in England, Wales, and Scotland. The Northamptonshire pilot consisted of five fixed camera sites and 45 mobile camera sites. Mobile enforcement was typically conducted on long stretches of roads known as red routes (corridors greater than 1 km). Enforcement took place at 10 sites where the speed limit was 60–70 mph. The costs associated with camera enforcement and processing of fixed penalty notices were collected for the first two years. Costs increased for year two, which may be due in part to the fact that not all of the sites were fully operational during the first year. In the second half of year two, the number of fixed penalties paid began to plateau, which may be due to increased compliance. In terms of enforcement history, the Northamptonshire area was comparatively new to camera enforcement.[67]		First year cost: £1,702,404 Second year cost: £2,247,838

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