REVIEW OF PRACTICES TO IMPLEMENT COST-EFFECTIVE ROADWAY SAFETY INFRASTRUCTURE IMPROVEMENTS TO REDUCE THE NUMBER AND SEVERITY OF CRASHES INVOLVING COMMERCIAL MOTOR VEHICLES

Executive Summary

Section 1113(b) of the Fixing America's Surface Transportation (FAST) Act requires the Secretary of Transportation to review, consult, and report best practices associated with implementing commercial motor vehicle (CMV)—related roadway safety infrastructure improvements. Safety is the top priority of the Secretary. According to the Center for Disease Control and Prevention, approximately 93 percent of all transportation-related fatalities are motor vehicle traffic crashes.⁽¹⁾ In 2015, 4,337 persons were killed in crashes involving large trucks or buses, based on data recently released by the National Highway Traffic Safety Administrations (NHTSA) Fatal Analysis Reporting System (FARS). This is 12 percent of all motor vehicle traffic fatalities. Due to the substantial weight differences between CMVs and smaller vehicles, these crashes often result in fatalities. Of those who died in 2015 as a result of crashes involving large trucks and buses, the recently released data indicates only 716 (16.5 percent) were occupants of the large vehicles, the remainder being occupants of other vehicles or pedestrians. Also of interest, from 2014 to 2015 there was a 4.1 percent increase in fatal crashes involving large trucks.⁽²⁾ Fatal truck crashes also have a significant economic cost, estimated to be more than $20 billion each year.⁽³⁾

However, CMV safety has improved in the last 30 to 40 years, both in absolute and relative terms. Fatalities in large truck crashes peaked in 1979 and have generally trended downward since then. The highest 5-year averages were just over 6,000 per year and have averaged around 3,900 in recent years, representing approximately a 35 percent reduction.⁽⁴⁾ At the peak levels of large truck crashes, the fatality rate for large truck crashes was almost double the rate for passenger vehicles (a rate of 6.15 fatalities in large truck crashes per 100 million vehicle miles traveled [VMT] by large trucks compared to 3.22 fatalities in passenger vehicle crashes per 100 million VMT by passenger vehicles).⁽⁴⁾ In recent years, these fatality rates are much closer. The lowest rate for large trucks was 1.17 in 2009, although that has continued to fluctuate, resulting in the current rate of 1.40 in 2014 when the passenger vehicle fatality rate was at a low of 1.05.⁽⁴⁾ This represents a measure of success for transportation safety professionals.

Improving CMV safety is also a goal of the National Multimodal Freight Policy. Trucks are a vital part of the multimodal freight system. The 11 million registered large trucks (single unit and tractor-trailer combinations) move the majority of freight shipments nationwide—69.6 percent of U.S. freight shipments by tonnage and 63.3 percent of shipments by value.⁽⁵⁾

CMV Safety Improvements

Continued improvements in CMV safety outcomes can be achieved through joint efforts between the Federal Motor Carrier Safety Administration (FMCSA), which enforces safety regulations for commercial carriers, and the Federal Highway Administration (FHWA), which oversees the infrastructure on which these vehicles travel. State and local agencies also play a key role because they maintain and operate that infrastructure. This report to Congress offers safety improvements (mainly infrastructure) to reduce both the number and severity of highway crashes; some are specifically designed for CMVs, and many address larger target crash types, which include CMVs as one of the vehicle types involved. This report groups the treatments reviewed into three primary categories:

Infrastructure safety. These improvements are most directly connected to the roadway infrastructure, including those that affect the roadway geometry, surfaces, or immediate roadside.

Communication infrastructure. These devices, either along the roadside or on the roadway, seek to communicate information to help CMV and other drivers safely navigate the roadway network. This includes warnings of traffic blockages (recurring congestion or incidents) that may increase safety risks for CMVs.

Innovative CMV safety practices. These practices to improve CMV safety include roadside intelligent transportation systems that increase compliance with safety regulations and provide for better separation of the larger and smaller vehicles to decrease the risks.

The safety improvements discussed in this report were selected from a review of literature and consultation with transportation practitioners. While the treatments included have all provided safety benefits to agencies that have used them and some are proven to reduce certain types of crashes, it is difficult to designate any particular improvement as a best practice since the benefits vary greatly depending on the highway system where it is applied (e.g., urban Interstate or rural two-lane road) and in some cases the specific location (e.g., intersection within a sharp curve with steep roadside slopes). The application of a given safety practice or crash countermeasure may require engineering studies or other analysis that is tailored to the roadway location. Therefore, some of these treatments may only make sense at very specific locations, whereas other treatments must be implemented over large portions of the highway network to achieve significant safety benefits. Within the report, each practice is assigned a readiness criteria of proven, tried, or experimental and the cost assessment is relative among the practices presented, using a five-part scale—high, moderate to high, moderate, low to moderate, and low cost.

Infrastructure Safety

Roadway Measures

The following safety features are applied to the roadway structure or immediately adjacent to it to mitigate safety risks for all vehicles, including CMVs:

• High-friction surface treatments (HFST) provide a highly durable aggregate locked firmly in place with a polymer binder that greatly increases friction in critical locations.
• Cross-slope break limits reduce the risk of rollovers for large vehicles on the outside of superelevated curves.
• Locations where water tends to pool may require additional drainage structures to remove precipitation or snowmelt.
• Higher-performance barriers can be more effective at containing or redirecting large vehicles.
• Rumble strips near the center line or edge of a lane can alert drivers that their vehicles are drifting from the travel lane, providing an opportunity for safe recovery. Onboard lane departure systems, or virtual rumble strips, perform a similar function.

Adding Lanes and Ramps

The following safety improvements expand the roadway footprint to mitigate the risks of CMV interactions with other vehicles in certain circumstances:

• Escape ramps provide drivers of large vehicles the opportunity to bring a runaway truck or bus to a safe stop by dissipating their energy.
• Climbing lanes and alternate passing lanes can decrease head-on collisions due to risky passing maneuvers in areas with limited sight distance.
• Interchange bypass lanes can separate large vehicles around or through a major interchange area, creating safer, easier merging lanes for CMVs.
• Exclusive truck roadways with various permutations have been studied to offer motor carriers the operational benefits of increased productivity, greater reliability, and safety benefits.

Communication Infrastructure

Signs and Signals

These safety treatments involve roadside communication of particular safety risks or operational conditions of concern to CMV drivers:

• Static warning signs alert drivers to a range of roadway conditions.
• Updating signs to Manual on Uniform Traffic Control Devices (MUTCD) standards to improve retroreflectivity and more uniformly apply curve signing.
• Dynamic warning devices display driver messages based on a broad range of vehicle behavior (speed, weight, and height) in advance of high-risk areas for CMVs and can be more effective than static signing to reduce crashes.
• Detection-control systems for traffic signals, which measure the speed and length of vehicles approaching an intersection to determine the best time to end the green phase, are particularly beneficial for large vehicles that take longer to come to a stop.

Pavement Markings

These safety-related communication treatments involve markings on the pavement because drivers regularly watch the pavement ahead for lane directions and possible obstructions:

• Horizontal signing can clarify lane assignments or simply provide emphasis to the driver about a roadway condition.
• Wider edge lines have been shown to reduce crashes on two-lane roads.
• Contrast markings improve lane marking visibility on concrete pavements, with possible benefits for fatigued CMV drivers.

Incident Warnings

This final class of safety communication treatments addresses CMV safety in higher-risk environments that may be sporadic or temporary, risks associated with aggregate traffic patterns that change, or weather-related conditions that pose risks to CMV operations:

• Queue detection warning systems in work zones monitor and detect queue buildup at critical transition points and display real-time warnings to upstream motorists.
• Work zone and incident electronic notification systems implement an in-cab alert system that notifies the CMV driver of an active work zone, traffic congestion, or an incident ahead.
• Visibility and wind detection systems alert drivers to infrequent but high risk driving conditions due to weather that can have serious crash consequences.

Innovative CMV Safety Practices

Compliance with Safety Rules

The following countermeasures are associated with roadside equipment that aids in inspection and enforcement activities or safety rules compliance:

• Parking systems provide information on available parking spaces to help commercial motor vehicle drivers comply with mandatory rest rules.
• Infrared braking detection systems have been tested that use roadside detection devices to identify overheating brakes. The devices have also been used to screen for other potential safety risks.
• Electronic screening deployed in advance of State roadside safety inspection facilities can electronically identify a CMV; verify its size, weight, and credentials information; and review the carrier's past safety performance, all while the vehicle is in motion.
• Virtual weigh stations can effectively target enforcement resources using unstaffed and remotely monitored roadside enforcement facilities.

Truck Separation Measures

States are experimenting with the use of regulatory measures to separate truck movements from the rest of traffic. The following two practices involve this kind of vehicle separation:

• Oversize/overweight (OS/OW) corridors can help manage common problems associated with OS/OW vehicle movements through regulatory authority and infrastructure improvements.
• Lane restrictions separate slow-moving trucks from faster-moving vehicles to improve traffic operations and to improve safety.

Gaps and Challenges

The future of CMV crash countermeasures may also be affected by a number of unpredictable trends:

• How freight and passenger economics and traffic will interact.
• How infrastructure design and safety treatments may evolve.
• How transportation technology may change CMV safety.

Future freight planning and highway safety planning, at the national and State level, will need to respond to these trends.

Future research can be considered by the transportation safety community to address issues as the FAST Act is implemented:

• Concerns about growing traffic levels of CMVs and passenger vehicles may lead to efforts to separate or segregate passenger vehicle and truck traffic. These infrastructure improvements could be balanced against changes in vehicle technology that add vehicle-based capabilities in both passenger vehicles and CMVs to keep both sets of drivers from human errors causing vehicle-to-vehicle crashes.
• As States designate highway freight networks as part of mandated State freight planning, linking State Strategic Highway Safety Plans (SHSP) to these corridors could help inform data-driven safety planning at the State level.
• The CMV safety improvements in this report are responsive to the current CMV fleet (even with regional size and weight variations authorized in current law). Statutory changes to size and weight restrictions may alter CMV safety outcomes and require different types of improvements or adjustment of existing countermeasures.

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