Smart Motorist

Improving Roadway Safety

Despite substantial progress in improving vehicles and driver performance, significant challenges remain to assure that the nation's roadways make their fullest contribution to the safety of road travel.

Even though road travel in this country is the safest of any industrialized nation, traffic crashes continue to extract a terrible toll in lives and property as reflected in the more than $150 billion burden they impose on our economy annually. This figure reflects the substantial societal costs of the fatalities, injuries, and property damage that occur but not their significant impacts on almost every aspect of our lives. Motor vehicle crashes create significant delays, increase road maintenance costs, contribute to air pollution, consume energy, and lower the productivity of the nation's industries and workforce. Moreover, they remain one of the greatest threats to public health we face. Despite substantial progress in improving vehicles and driver performance, significant challenges remain to assure that the nation's roadways make their fullest contribution to the safety of road travel.

The objectives of this report are to identify major roadway safety issues presently confronting communities across the nation and to lay the foundations for state and local governments to implement solutions. It is intended for persons who do not have a background in transportation engineering, but are interested in ensuring that road transportation is safe and efficient. Audiences for whom this report has been prepared include concerned citizens and advocacy groups, as well as state and local government officials.

Resolving safety and infrastructure problems has always been limited by available resources, but opportunities to increase emphasis on these issues are afforded by the upcoming reauthorization of federal highway and transit programs. It is the Roadway Safety Foundation's hope that this report can make a contribution to the public policy debate by identifying the most significant roadway safety issues and making the case for increased expenditures on safety as a national priority. Many potential countermeasures (solutions) already exist and could be implemented if resources were provided. New countermeasures, derived from emerging technologies, could lead to significant safety improvements if funds were available to develop and implement them.

The Roadway Aspect of Safety

The safety of road transportation is a product of the interactions between the driver, the roadway and the vehicle. Advances in the design of vehicles, improved driver performance, and enhancement of the roadway have all contributed to the level of safety we presently enjoy. While each of these elements contributes to the ultimate safety provided by our road transportation system, this report focuses on enhancements to the roadway as a means of further improving safety.

Needed Roadway Safety Improvements

Safety improvements are needed on all types of roads interstates, multi-lane highways, and two-lane roads. Interstate highways the "workhorse" of the highway network carrying 23% of all roadway travel and 45% of large truck traffic are not immune to safety problems. Design standards used on the Interstate have contributed greatly to its low highway death rate of .74 per hundred million vehicle miles of travel. Effective highway operations have kept these critical transportation arteries available and free flowing, further contributing to their lower fatality and injury rates. Economist Wendell Cox estimates that the Interstate saved approximately 187,000 lives and prevented 11.8 million injuries over its 40 years of existence. Changes in the size, design and mix of today's vehicles - larger trucks, lighter cars, pick-ups and sport utility vehicles are challenging the effectiveness of current highway designs. For example, the width of current Interstate medians is being questioned due to an apparent increase in cross-over accidents. Interstate access ramps may not safely accommodate all types of motor carriers currently operating on the system. To address these safety problems, significant investments will be needed, in addition to the funds required to maintain current conditions on the Interstate. (The Department of Transportation estimates that maintaining current conditions will cost $10.1 billion a year for the next twenty years.) At the other end of the spectrum are the two-lane roads which represent over 40% of the National Highway System and more than 75% of the entire national road network. Many two-lane roads were constructed before current safety guidelines were developed and face problems resulting from traffic levels well beyond those anticipated, particularly at the outskirts of urban areas. The death rate for non-federal roads which are frequently two lanes exceeds 2.3 per hundred million vehicle miles of travel. Crashes on these roads have more serious consequences because of narrower lanes, hazardous roadsides, steeper grades, and sharper curves.

Changing Conditions

Changing conditions make it necessary to continually monitor roadway safety. Changes in traffic, technology, environmental conditions, and fleet characteristics influence safety problems and their solutions. Today's growing traffic volumes increase everyone's potential exposure to accidents. Inadequate maintenance and improper installation of safety features such as guardrails and barriers are potential safety problems on all highways. Increased truck sizes, higher centers of gravity for vans, pick-ups, and sport utility vehicles, new headlamps, and aerodynamic vehicle designs (e.g., sloped front ends) are often incompatible with the roadway and associated traffic control and safety features. The very changing nature of these factors continually raises questions about the adequacy of current countermeasures and highway design standards. An aging driver population, reduced compliance with traffic regulations, higher traffic speeds, aggressive driving behavior, and demands for use of the road by pedestrians and bicyclists pose additional challenges. Environmental concerns make it difficult to remove a tree close to the edge of a roadway or widen lanes adjacent to streams or lakes. Consequently, there is a need to continually work to fill gaps in knowledge and provide this information to decision-makers and persons responsible for highway safety at all levels of government. The Roadway Safety Foundation hopes to play a role in this area.

Major Safety Problems

The Roadway Safety Foundation conducted an extensive review of the technical literature of the past twelve years to identify major safety issues associated with the roadway. Safety issues identified in this effort include crashes resulting from:

Roadway Departure - Crashes resulting from simply leaving the roadway, regardless of underlying cause, represent a substantial portion of the total crash problem. They occur on both straight and curved sections and often involve either rollover of the vehicle or collisions with fixed objects such as trees, utility poles, etc.
Road Surface Conditions - Aberrations in the road surface such as pavement edge drop-offs, "potholes" and reductions in surface friction due to age and wear affect vehicle stopping and maneuvering capabilities. Also includes temporary conditions related to ice or snow.
Narrow Roadway Cross Sections - The width of each travel lane, the presence of a road shoulder, and their basic construction characteristics are all important to road safety. The travel lane defines the space in which drivers have to perform all maneuvers common to driving in a safe manner. In general, wider lane/shoulder combinations are safer. Shoulders provide 'buffer' space and a place for disabled vehicles to stop clear of traffic.
Narrow Bridges - Bridges whose width is less than that of the approaching travel lanes and shoulders are a known cause of crashes. While they are relatively infrequent, they are often severe. Collisions result from vehicles striking the ends of bridges, guardrails, curbing, or vehicles traveling in the opposite direction.

Other safety problems exist at intersections and interchanges, railroad crossings, work zones, and in growing commercial and residential areas where access management issues are critical. Future efforts may focus attention on these safety problems as well.

Addressing Safety Problems

Countermeasures for addressing highway safety problems take many forms ranging from educating the driver, enhancing the safety features of vehicles, to improving the roadway and its environs. They fall into two major categories - those designed to prevent crashes from occurring and those which minimize the severity of crashes that do occur. Roadway problems may require major reconstruction but often significant safety improvements can be realized from lower cost countermeasures. Decisions on the most appropriate countermeasure must be made recognizing the many fiscal and political constraints within a community, but it is important to know the full range of options available. Community leaders can then make informed decisions about the best way to reduce the adverse impacts of crashes on the people they serve. Representative countermeasures for the major safety problems identified include:

Countermeasures for Roadway Departure Crashes

Clear Zones - Areas of open space adjacent to the road giving motorists room to safely regain control of their vehicles if they run off the road.
Gradual Side Slopes - Gentle slopes along the roadway create less risk of vehicles over-turning if they leave the road and help drivers regain control.
Forgiving Devices - Roadway features such as signs and utility poles which breakaway on impact, barrier walls or guardrails which redirect vehicles away from hazards, crash cushions which absorb energy, lessen the severity of crashes.
Rumble Strips - Regular undulations in the paved surface along the edge of the roadway provide an auditory and tactile signal to alert drivers encroaching on the road shoulder or approaching some other potentially hazardous situation.
Signing, Pavement Marking, and Delineation - Traffic signs, pavement markings, and reflective devices improve driver perception of important roadway features and alert them to changes in roadway geometry or other conditions.

Countermeasures for Crashes Involving Road Surface Conditions:

Increased Surface Friction - Greater road surface friction provides drivers with increased traction for maneuvering and stopping.
Temporary Friction Enhancement - Greater roadway friction is provided for increased traction in adverse weather conditions, particularly snow and ice.
Pavement Improvements - Greater smoothness and friction of the road surface are provided by resurfacing, rehabilitation, and reconstruction.
Stabilizing Shoulders - Improvements in the stability of the material covering roadway shoulders help drivers control their vehicles and return to the roadway.
Preventive Maintenance - Maintenance can eliminate drop-offs between the road pavement and shoulder or adjacent lane that can cause drivers to lose control when attempting to return the vehicle to the road surface. Regular maintenance to repair "potholes" can eliminate erratic maneuvers by motorists.

Countermeasures for Narrow Roadway Crashes:

Widening Lanes - Wider lanes provide a larger road surface on which to maneuver in an emergency without leaving the road surface.
Adding or Widening Shoulders - Shoulders provide drivers with additional room to maneuver on narrow roads.
Channelization - Separate lanes for left or right-turning traffic avoid impediments to traffic flow which can lead to rear end crashes.
Pedestrian/Cyclist Facilities - A variety of techniques can be used to separate pedestrians and cyclists from motor vehicle traffic to improve safety.

Countermeasures For Narrow Bridge Crashes:

Widening Bridges - Twelve foot lanes are preferable. Additions of shoulders can further enhance safety.
Bridge Treatments - The addition of safety features such as crash cushions or guardrails as transitions to the bridge ends reduce crash severity.
Signing, Pavement Marking, and Delineation - Signs and pavement markings alert drivers to approaching narrow bridges and allow them to position their vehicles most safely when crossing bridges.

Other countermeasures exist beyond those highlighted. The Roadway Safety Foundation acknowledges the need to compile and maintain comprehensive information on countermeasures, particularly as new options emerge, and the latest guidance on where they can most appropriately be used. Equally important, the Foundation must implement strategies for communicating this information effectively to those concerned with improving highway safety. It is our hope that this report will be helpful to decision makers in assessing various countermeasures and allocating limited safety funds most effectively.

Gaps in Knowledge

The Foundation's initial review of roadway safety research shows that despite a large volume of work in this area, there are substantial gaps in our knowledge of safety issues and the factors affecting them. They are so substantial that they inhibit our ability to increase the safety of road travel. Some of these gaps relate to particular types of roads, others to the impact or effectiveness of countermeasures, or the ability to monitor changes in safety. Principal gaps include:

Sufficiently Detailed Safety Data - There are simply no data systems which capture all of the crash and roadway information needed to address many road safety issues. Without this information we can not be certain of the significance of particular safety issues and the effectiveness of measures which are implemented to prevent them.

Effects of Changes in Fleet Mix and Vehicle Characteristics on Safety-Vehicles are becoming larger, possess different front end profiles, and differ substantially in many of their handling characteristics, all of which have the potential for adversely affecting the benefits obtainable from existing roadway safety features. Further improvements in safety will require that we understand the implications of these changes for the design of existing safety features as well as those emerging from research laboratories.

Effectiveness of Safety Treatments - There is limited information about the effectiveness of individual or combinations of countermeasures. Without such information, it is difficult to make informed choices about the most appropriate countermeasures for a specific situation.

Relationship between Roadway Design and Safety - Recent research studies concluded that there is only limited understanding of the impact on safety of basic roadway design elements, particularly for multi-lane highways. More precise quantitative relationships need to be established between safety and specific features such as median widths, alignments and sight distance at intersections, etc. In addition, the combined effect of multiple design features is not well understood.

A significant number of research and development efforts are underway which will help fill the gaps in knowledge that exist and promote improvements in highway safety. The Roadway Safety Foundation expects to monitor these efforts, promote continued research, and share this information with decision-makers and community leaders committed to improving roadway safety.

Related website: http://www.roadwaysafety.org/

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