Statistical Models of At-grade Intersection Accidents

DTFH61-92-C-00031The objective of this research was to develop statistical models of the relationship between traffic accidents and highway geometric elements for at-grade intersections. These models also incorporated the effect of traffic control features and traffic volumes on intersection accidents. The data base used to develop the models was obtained from the California Department of Transportation. Field data were also collected for a sample of urban, four-leg, signalized intersections to provide data on additional geometric design variables and turning-movement counts that were not available from existing highway agency files. The statistical modeling approaches used in the research included Poisson, lognormal, negative binomial, and logistic regression, as well as discriminant and cluster analysis. Regression models of the relationships between accidents and intersection geometric design, traffic control, and traffic volume variables were found to explain between 16 and 38% of the variability in the accident data. However, most of that variability was explained by the traffic volume variables considered; geometric design variables accounted for only a very small additional portion of the variability. An evaluation of hard-copy police accident reports by three independent reviewers for a sample of eight urban, four-leg, signalized intersections found that only 5 to 14% of the accidents had causes that appeared to be related to geometric design features of the intersections

Accident and Speed Studies in Construction Zones

DOT-FH-11-8121The report includes results of two studies of construction zone traffic control. The first study involved analysis of traffic accidents occurring in 79 zones in seven states. Results indicate a before to during accident rate increase of 6.8%. Results also include breakdowns by accident types, severity, light conditions, roadway type, area type, work area roadway type, construction type and state. The second study was field testing of speed reduction methods. Speeds, erratic maneuvers and conflicts were measured at three sites--an urban freeway, a rural freeway, and an urban street. The field studies examined the effect of the following construction zone parameters on vehicle speeds and safety: Sequential flashing arrow boards; speed zoning (advisory and regulatory); enforcement; transverse striping; obliteration of nonappropriate pavement markings; taper length; lane width reduction; and active warning of speed zoning. Recommended guidelines for construction zone traffic controls are also included

Truck Characteristics for Use in Highway Design and Operation. Volume I: Research Report

DTFH61-87-C-00088Highway geometric design and traffic operations are based in part on consideration of vehicle characteristics. However, many of the current highway design and operational criteria are based on passenger car characteristics, even though truck characteristics may be more critical. This report reviews existing data for the truck characteristics that need to be considered in highway design, including truck dimensions, braking distance, driver eye height, acceleration capabilities, speed-maintenance capabilities on grades, turning radius and offtracking characteristics, suspension characteristics, and rollover threshold. The report also includes these truck characteristics. The highway design and operational criteria evaluated include sight distances, vertical curve length, intersection design, critical length of grade, lane width, horizontal curve design, vehicle change intervals at traffic signals, sign placement, and highway capacity. An assessment has been made of the need to change the current highway design and operational criteria to accommodate trucks. The cost effectiveness of proposed changes in design and operational criteria has been evaluated. This volume, Volume I, of the report presents the main findings of the study including recommended changes in highway geometric design and operational criteria to accommodate trucks. Volume II of the report contains appendixes documenting the detailed data collection and analysis activities

The thermal performance of earth covered buildings in hot, arid regions /

"Work Performed Under Contract No. EG-77-C-01-4042.""October 1980."Includes bibliographical references.Mode of access: Internet

Passing Lanes and Other Operational Improvements on Two-Lane Highways

DTFH61-82-C-00070Many two-lane highways in rural areas experience operational problems related to high traffic volumes; lack of adequate passing opportunities; slow-moving vehicles on grades and in rolling terrain; roadside development that generates turning maneuvers at driveways; and turning movements at intersections. This report evaluates five operational aids or treatments intended to alleviate these problems including: passing lanes, short four-lane sections, shoulder use sections, turnouts, and two-way left-turn lanes. The report reviews current signing, marking, and design practices used for these operational treatments in 13 states that participated in the study. An operational evaluation of the treatments was based on field data collected at 35 treated sites. Safety evaluation of these treatments was based on accident data collected at 138 treated sites. The study concluded that each of the five types of operational treatments that were evaluated can be effective in improving traffic operations on two-lane highways. Passing lanes, short four-lane sections, and two-way left-turn lanes were also found to improve safety while turnouts and shoulder use sections were found to have no effect on safety

Indium phosphide/cadmium sulfide thin-film solar cells : quarterly report for period July - October 1980 /

"Work Performed Under Contract No. AC02-77CH00178.""Contract XZ-0-9196-1.""January 1981."Mode of access: Internet

Zn₃P₂ as an improved semiconductor for photovoltaic solar cells : ninth quarterly report for September 1 - November 31, 1980 /

"Work Performed Under Contract No. AC02-77CH00178.""Subcontract no.Mode of access: Internet

Thin film polycrystalline silicon solar cells : first technical progress report for April 15 - July 15, 1980.

"Work Performed Under Contract No. AC02-77CH00178.""July 1980."Includes bibliographical references (page 22).Mode of access: Internet