Experimental Plans for Accident Studies of Highway Design Elements: Encroachment Accident Study

DTFH61-92-C-00172This report documents an investigation into the feasibility of using accident data to derive estimates of the rate at which errant vehicles unintentionally encroach into the roadside on level, tangent sections of two-lane rural roads. In addition, issues related to estimating the percentage of unreported accidents were also investigated. The report discusses results from the literature and an analysis of hit-utility-pole accident cases from the National Accident Sampling System (NASS). A pilot study involving 56 km (35 mi) of tangent, two-lane rural road sections in Idaho is also documented. For that pilot study, detailed roadside data were collected and accident and traffic data were obtained. Based on an analysis of that data, the resulting encroachment rate estimates were determined to be of the same order of magnitude as the encroachment rates that had been developed from previous research. It was concluded that the methodology is feasible, although it is limited by the current state of the knowledge with respect to data on the trajectories of vehicles involved in run-off-the-road and hit-fixed-object crashes. An experimental plan for future research that would produce improved estimates of roadside encroachment rates is also presented. Because the plan depends on the availability of detailed sign maintenance and roadside inventory data in electronic media, it is recommended that the plan not be implemented immediately. When and if it is implemented, the latest results from other research on trajectory data should be integrated into the plan

Removal of Multiway Stop Signs with Minimum Hazard, Volume I: Technical Report

DTFH61-82-C-00029This study reports on the experience of more than 30 political jurisdictions throughout the United States which have converted multiway, stop sign-controlled intersections to lesser forms of controls. In all instances, those officials interviewed during field visits reported converting 4-way or 3-way stop intersections to 2-way or 1-way stop intersections. A great variety of procedures and accompanying notice, caution, and warning signs were found to have been used in the conversion of the more than 172 intersections studied. Generally, low volume, low speed, residential intersections were being converted safely without the use of supplementary signs. As intersection volumes increased, there was an increased need for multiway stop sign-intersection conversion aids. Procedures were developed by which multiway stop sign-controlled intersection can be converted to lesser forms of control with minimum hazard. Signs installed prior to the conversion. Signs placed under the remaining stop signs after conversion should read "CAUTION, CROSS TRAFFIC DOES NOT STOP." Any stop line pavement markings on the new through street should be removed. Volume I reports on the overall study effort. Volume II addresses details of the recommended conversion procedures for use as a guide by local officials

Older Driver Perception-Reaction Time for Intersection Sight Distance and Object Detection, Volume I: Final Report

DTFH61-90-C-00038Four on-road experiments investigated whether the assumed values for driver perception-reaction time (PRT) used in AASHTO design equations adequately represent the range of actual PRT for older drivers. The Case III (stop controlled) intersection sight distance (ISD) experiment found that older drivers did not have longer PRT than younger drivers; 85th percentile PRT closely matched the AASHTO design equation value of 2.0 s. In the stopping sight distance (SSD) experiment involving brake reaction times to an unanticipated event (crash barrel suddenly rolling toward roadway), there were apparent differences in the distribution of PRT among age groups. Younger drivers accounted for most of the fastest PRT, but there were no age differences in the 50th or 85th percentiles. All observed PRT were encompassed by the current AASHTO design value of 2.5 s. The decision sight distance (DSD) experiment measured when drivers recognized the need to make a lane change maneuver, from the first visibility of the roadway cue used by the driver. Although observed DSD values were generally longer with increasing driver age, the 85th percentile PRT for all age groups were well below AASHTO design assumptions. The final experiment collected judgments about the acceptability of gaps and lags in traffic. Younger subjects accepted shorter gaps and rejected lags later than older subjects. Based on these findings, and consideration of the implications of changes in PRT for sight distance requirements, no changes to design PRT values, based on older driver performance, were recommended for ISD, SSD, or DSD. Alternative models for ISD, based on gap acceptance or lag rejection, were explored. Based on limited data, it is not clear whether these models offer any significant benefits to the current AASHTO model

Feasibility of an Automatic Truck Warning System

DTFH61-91-R-00069One of the identified truck accident types that occur on curved exit ramps at interchanges is truck rollover. A truck will overturn or rollover if the lateral acceleration imposed upon it as it travels around a curve of a certain radius and superelevation is greater than allowable given its loading condition. Also, there is a speed at which rollover will occur. This report deals with an automatic warning system to prevent truck rollover. Within the study, three different options were identified and evaluated for feasibility. Of the three, the option selected for further definition and cost-effectiveness analyses was an inroad detection/warning system. The system consists of two detection stations upstream of the curve with the combined ability to detect a truck speed, weight, and height threshold. The warning system is a combination of a static warning sign and a fiber-optic warning message sign, which would be activated if the controller determined that the truck would be operating at the rollover threshold speed or faster by the time it reached the point of curvature. This report provides the details of the design, its costs, and its cost-effectiveness. Also, design plans and specifications were prepared for three installations on the Capital Beltway in Maryland and Virginia

Development of a large truck safety data needs study plan. Volume II - technical report. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Bellomo-McGee, Inc., Vienna, Va.Report covers the period Aug 1984 - Feb 1986Subject code: DEFSubject code: WLSubject code: WMEGSubject code: WT

Development of a large truck safety data needs study plan. Volume I - summary. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Bellomo-McGee, Inc., Vienna, Va.Report covers the period Aug 1984 - Feb 1986Subject code: DEFSubject code: WLSubject code: WMEGSubject code: WT

Alternative experimental designs to evaluate alternative edgeline widths on two-lane rural roads. Final report.

Federal Highway Administration, Office of Safety and Traffic Operations Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Bellomo-McGee, Inc., Vienna, Va.Subject code: CCCCCSubject code: CCJSubject code: CDFNSubject code: CICSubject code: SCE*

Highway design and operations standards affected by vehicle characteristics. Final report.

Federal Highway Administration, Office of Safety and Traffic Operations Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Bellomo-McGee, Inc., Vienna, Va.Report covers the period Sept 1982 - Dec 1984Subject code: CGSubject code: CGDSubject code: NCYS*DPCSubject code: NRLSubject code: WOB*

Visibility requirements of work zone traffic control devices. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: BioTechnology, Inc., Falls Church, Va.Report covers the period March-July 1978Subject code: CDNCSubject code: HBESubject code: NDGSubject code: PMK