Brian L Bowman

COST- AND LONGEVITY-BASED SCHEDULING OF PAINT AND THERMOPLASTIC STRIPING

Because no national guidelines exist on establishing pavement marking service life, the scheduling of road striping has been inconsistent among maintenance agencies. This study establishes a way to set striping schedules that accounts for factors affecting scheduling, mainly application cost, service lifetime, and user cost relative to crashes during the striping lifetime. Striping useful lifetime is defined as the striping age beyond which pavement markings become ineffective in relaying necessary vehicle positioning information, when deteriorated pavement marking retroreflectivity reaches a minimum acceptable value. An exponential regression model was used to depict the relationship between striping age and average daily traffic (ADT), using a retroreflectivity threshold of 150 mcd/m2/1x. Striping useful lifetime was established for ADT levels using exponential regression analysis. Application costs were based on the latest available unit costs from the Alabama Department of Transportation for white and yellow longitudinal stripes of paint and thermoplastic markings. Using the National Safety Council estimates of crash severities, user costs were based on the dollar equivalency of the damage to vehicles and occupants in retroreflectivity-related crashes. The data were extracted from the crash experience of approximately 1,300 mi (2100 km) of state highways in 32 Alabama counties. For use in scheduling striping, paint and thermoplastic striping costs were compared on an equivalent annual basis, accounting for application and user costs. Although the crash data and retroreflectivity data were collected on Alabama roads, the findings and conclusions are applicable to areas of warmer climate where snowfall is uncommon.

PLAN OF ACTION TO REDUCE VEHICLE-TRAIN CRASHES IN ALABAMA

In April 1996, the state of Alabama Legislature, through the passage of Act 503, directed the Alabama Department of Transportation (ALDOT) to conduct a comprehensive study of rail-highway grade crossings in the state and recommend methods to drastically reduce the number of vehicle-train crashes. Senate Act 503 states: “… That the Alabama Department of Transportation is directed to conduct a comprehensive study of the rail/highway grade crossings in the state and present a plan to this body recommending methods to dramatically reduce vehicle/train accidents by the first day of the 1997 Regular Session.” In response to Act 503, the Multimodal Bureau of ALDOT developed an Action Plan that compared Alabama’s grade crossing crash experience with the experience of the national and southeastern states to identify the prevalent characteristics, identified the perceived needs of safety and railroad professionals required to decrease vehicle-train crashes and crash severity, and compiled a list of recommendations and activities required for implementation. The activities and results of the Act 503 study documented in the final report are summarized (1). It discusses the engineering, economic, educational, enforcement, and emotional impediments to increasing rail-highway intersection safety and presents a broad range of realistic countermeasures. These countermeasures include legislative action; judicial reform; and enforcement, economic, and education initiatives.

Initial Ride Quality of Hot-Mix Asphalt Pavements

Ride quality assessed with an inertial profiler on flexible pavement was used to provide initial information on the following key issues: repeatability associated with international roughness index (IRI) values for a wide range of hot-mix asphalt (HMA) material variables, timing of acceptance testing for initial ride quality, IRI changes with type of roadway, influence of stops and starts in the paving operation on ride quality, identification of “bump,” and effect of grinding on IRI. IRI was calculated for 25-ft intervals instead of the standard 0.1 mi (528 ft) for all testing to highlight local anomalies such as bumps due to paving stoppages. Results indicate that the standard deviation of three replicate passes with an inertial profiler is 5 in./mi (includes 46 HMA mixes on the Auburn University National Center for Asphalt Technology test track). IRI measurements with time suggest that initial acceptance testing can be conducted within 7 days, which allows more flexibility in scheduling by the agency. Limited traffic also slightly reduces the IRI values, which is to the contractors advantage. IRI values are suggested for two-lane county roads and medium- to high-traffic facilities. Separate IRI ranges are indicated for each of these categories on the basis of the type of HMA construction: new, repair and overlay, and mill and overlay. These ranges are set for best and good practices (continuous paving, no stoppages; consistent supply of trucks, very short stops). IRI values greater than 125 in./mi in any given 25-ft interval indicate a bump; bumps can be ground so that these areas have IRI values of less than 100 in./mi.

Analysis of Handicapped Parking at Auburn University

The number of handicapped spaces that serve a facility is largely determined on the basis of Americans with Disabilities Act of 1990 (ADA) guidelines, which do not take into consideration the actual land use that a parking lot serves. The ADA guideline of basing the number of handicapped spaces on the size of the parking lot does not work well for land uses such as universities. The following study looks at the campus of Auburn University in order to develop a model that will base the number of handicapped spaces on the characteristics of the facility the parking lot serves. Models were developed with occupancy rates, turnover rates, and facility characteristics as variables. A model based on the peak period occupancy rates was used to determine the recommended number of handicapped parking spaces. Using the peak period occupancy rate generates the proper number of spaces required to accommodate the demand.

Impediments to and methods for evaluating safety management systems

The Intermodal Surface Transportation Efficiency Act (ISTEA) mandates that individual states develop six transportation infrastructure management systems. One of these systems, the safety management system (SMS), focuses on reducing the number of roadway traffic accidents, injuries, and fatalities by considering the safety needs of the driver, vehicle, and roadway. This necessitates cooperation among state, city, and county roadway agencies as well as diverse public and quasipublic agencies. States have made significant advances toward implementing SMSs. The safety community recognizes that it is time to coordinate safety activities and responsibilities. Even if it is not mandated by Congress, as recent actions indicate, a large number of states are expected to implement elements of their SMS work plan. With this implementation comes the need for the evaluation of SMSs effectiveness in increasing traffic safety and ultimately reducing the number and severity of accidents. The challenge in evaluating SMS ...

Computerized office support for state highway-rail crossing programs

State programs in grade crossing safety are an important and successful traffic safety initiative. Their cost-benefit ratios are close to those achieved on all other highway safety projects. Estimates suggest these railroad crossing improvements have contributed to an 88 percent reduction in fatalities and a 62 percent reduction in injuries. While these achievements were obtained through the combined efforts of railroad companies and federal, state, and local governments, the primary responsibility for carrying out the program has fallen upon the states. States have developed individual procedures in identifying and improving high-risk grade crossings. These procedures, which constitute a naturally collaborative process, often lead to long periods of time between the initial identification of high-risk crossings and the physical installation of improvements. Most states either have initiated action or are considering procedural changes to reduce these times. One particularly beneficial action is a status ...