1. NCHRP 20-07 Task 303  DIRECTORY OF SIGNIFICANT TRUCK SIZE AND WEIGHT RESEARCH

2. MOTIVATION Decision-makers are challenged to identify/utilize state of knowledge from truck size and weight research Extensive volume of related research, dating back nearly 80 years Breadth of related topic areas including infrastructure preservation, enforcement, safety, congestion, environment, industry costs, modal share, etc. Diverse interests of public and private sponsoring agencies/ organizations

3. OBJECTIVE To develop a “directory” of significant truck size and weight research that is brief, well-organized, and neutral Address the breadth of all related topic areas Consider research performed by various sponsoring agencies Be organized topically with embedded cross-references directing readers to additional findings NOT be inclusive of all related research Only essential information is included. Each finding is carefully cited to support additional information gathering.

4. TECHNICAL APPROACH Task 1:Distinguish Relevant, Significant, Useful Research from Body of Research Timeliness Soundness of the methodology Scope and comprehension Conducted in response to an expressed need Task 2:Extract Key Research Findings Methodological strengths or shortcomings that may influence validity of findings Trends or commonalities among publications that suggest a higher level of confidence Conflicting findings that challenge decision-making Task 3:Produce Final “Directory of Significant Truck Size and Weight Research”

5. FINDINGS Infrastructure Preservation –Pavement –Bridge Modal Share Enforcement Highway Safety Highway Geometrics Industry Costs Infrastructure Financing Highway Congestion Environment Public Opinion

6. MODAL SHARE Complex, profit-driven, economic relationships –Increased truck limits lead to lower truck transport costs –Industry competition and regulatory pressure translates lower costs into lower transport rates –Rail industry must either match lower rates or lose freight traffic—in either instance, rail revenues will decline Estimates of traffic diversion/rail revenue losses are highly variable and sensitive to –Regional commodity movement/infrastructure conditions –Extent of truck payload capacity increases –Evaluation assumptions

7. MODAL SHARE Shippers consider price and service –Rail service is almost always less expensive –Truck service offers faster, door-to-door delivery –For low-value commodities—such as coal, grain, or chemicals—price is often a priority over service Highest levels of modal competition exist for –Intermodal operations with combined truck/ rail transport –Carload operations that utilize boxcars

8. ENFORCEMENT Challenged to accurately relate enforcement and compliance –Reliable estimates of illegal activity are lacking –Wide divergence in U.S. enforcement practices Higher enforcement levels generally associated with higher compliance –Violation rates for fixed Interstate weigh stations <1% when enforcement is present 15% when it is not –Violation rates along bypass routes and/or using mobile enforcement are higher in frequency (30%) and magnitude

9. ENFORCEMENT Combination of fixed and mobile enforcement can be most effective Greater reliance on technology provides increased spatial/temporal coverage with personnel constraints Laws/regulations that are complex or contain numerous exceptions challenge enforcement and subsequent prosecution

10. INDUSTRY COSTS Increased truck size and weight limits consistently result in estimated industry cost savings Magnitude of cost savings varies by –carrier type –nature of transportation services offered –commodities transported Truckload carriers and low density cargoes benefit most from larger truck sizes Estimated industry cost savings range from 1.4 to 11.4 percent of annual U.S. transport costs

11. INFRASTRUCTURE FINANCING Predominant truck-focused alternative financing strategies include –Tolled facilities –Weight-distance based road user fees –Container and/or U.S Customs and Border Protection fees Industry is highly fragmented—any alternative financing strategy will likely evoke varied reactions With some consistency, industry favors truck-only tolled or shared facilities that provide operational advantages (e.g., increased size or weight limits) –Toll facilities that offer only congestion avoidance benefits are insufficient in overcoming increased operating costs

12. INFRASTRUCTURE FINANCING Weight-distance based road user fees are commonly based on registered not actual truck weights –Levies on registered GVW may promote higher logistical efficiency by discouraging “empty” trips, but this effect has not been considered or reported in the literature –Current technology (WIM systems) allows capture of actual weight, making fees more equitable in terms of potential infrastructure damage –Weight-distance based road user fees have been demonstrated to generate more revenue than mileage- based registration fee systems

13. HIGHWAY CONGESTION Larger, heavier trucks can affect highway congestion by –Decreasing heavy truck VMT with increased truck capacity –Increasing heavy truck VMT in response to lower transport costs –Decreasing highway capacity as a result of compromised maneuverability and less horsepower relative to weight Larger, heavier trucks are predicted to modestly degrade traffic flow and capacity—anticipated reductions in heavy truck VMT likely offset these negative impacts Prior studies have been criticized for oversimplifying interactions between trucks and other vehicles

14. PUBLIC OPINION Public opinion is largely shaped by safety-related media campaigns –Despite marked improvement over time, majority of drivers express safety concerns regarding large trucks Based on limited studies, increases in truck size rather than weight are of more concern –Increased truck size—particularly length—is more visible and perceived to affect safe passing maneuvers and truck driver visibility –Incremental changes in truck weight will likely not affect survivability in a collision

15. PUBLIC OPINION Majority prefer status quo on Federal truck size and weight limits—or a return to more restrictive limits if any changes are to be made Enforcement of existing truck size and weight regulations perceived to be inadequate –Public lacks confidence that any increased limits could be controlled

16. QUESTIONS