Roadway Type Research Articles

Retroreflective Material Specifications and On-Road Sign Performance

Retroreflective materials for traffic control devices are designed to return light from a vehicle’s headlamps back to the driver. Recent advances in material technology have created prismatic retroreflective sheeting. This type of material does not have the predictability in its retroreflective performance of the older, glass-bead material. The ASTM recently recognized three new types of prismatic material for traffic control devices. The on-road performance of these new material types was examined through the use of computer simulation of sign luminance. Inputs to the computer model included vehicle dimensions, headlamp illumination data, material retroreflectivity data, sign placement, and roadway geometry. A variety of sign positions and roadway types was included to illustrate the similarities and differences among the three new types of material. The ranking of the three materials in terms of sign-luminance performance depends on the roadway configuration and the viewing distance. ASTM Type VII is shown to be comparable to Type VIII at long distances with small entrance angles but superior to Type VIII and IX in large entrance-angle situations. ASTM Type IX is shown to have higher luminance at shorter distances associated with sign-legibility distance ranges. Engineers and specifiers are encouraged to evaluate on-road sign performance at night before making material choices.

Service Life of Durable Pavement Markings

The service life of durable pavement markings was evaluated over a period of nearly 4 years. The evaluation included 85 study sites in 19 states at which a total of 362 longitudinal pavement marking lines (edgelines, centerlines, and lane lines) were installed. Marking materials included epoxy, flat and profiled polyester, flat and profiled poly(methyl methacrylate), flat and profiled thermoplastic, and profiled preformed tape; glass beads; and standard and snow-plowable raised retroreflective pavement markers. One site with conventional paint markings and three sites with waterborne paint markings were included for comparison. The service life of marking materials and roadway types was modeled as a function of time and cumulative traffic passages. Regression modeling identified large variations in the shape of the relationship for identical materials and types of lines between different sites within a given state and required that modeling be done separately for each pavement marking line at each study site. Variations in service life can be attributed to roadway type, region of the country where the markings were installed (e.g., weather conditions, manufacturers of marking materials and glass beads, and individual state highway agencies), marking specifications, contractors installing the markings, quality control at the time of installation, and winter maintenance snow removal policies.

Definition of the Light Vehicle Off-Roadway Crash Problem for the Intelligent Vehicle Initiative

Off-roadway crashes involving light vehicles (passenger cars, sport utility vehicles, vans, and pickup trucks) were analyzed based on the 1998 General Estimates System crash database to support the development of countermeasure systems as part of the U.S. Department of Transportation’s Intelligent Vehicle Initiative. An off-roadway crash occurs when a vehicle in transport departs the road due to loss of control or crossing the edge of the roadway. Approximately 924,000 such crashes occurred in the United States in 1998. These crashes are grouped into six distinct precrash scenarios (3 × 2 matrix) based on vehicle movements (going straight, negotiating a curve, or initiating a maneuver) and critical events (departed roadway edge or lost control). These scenarios are described statistically in terms of their physical setting, which consists of the roadway type, land use, relation to junction, number of travel lanes, and speed limit. Moreover, factors that might have contributed to the cause of these crashes are identified. According to this analysis, 85 percent of these off-roadway crashes occurred on nonfreeways, 64 percent in rural areas, 83 percent away from junctions, 60 percent on two lanes of travel, and 62 percent below the 89-km/h (55-mph) speed limit. In addition, speeding and alcohol were reported in 25 and 20 percent of these crashes, respectively. Finally, inclement environmental conditions or driver inattention or distraction might have contributed to about 42 percent of these crashes.

Modeling vehicle headways for low traffic flows on urban freeways and arterial roadways

One of the important microscopic flow characteristics that affects safety, level of service, driver behavior, and capacity of the roadway is vehicle headway. The time between arrivals of successive vehicles passing a point on roadway is called vehicle headway. This study aims at analyzing the vehicle headway for urban freeway and arterial roadway sections in Riyadh (capital of Saudi Arabia) and comparing them with results from international research. Only low volume traffic conditions is of the concern in this research. The paper describes the mathematical distribution for vehicle headway data on two types of roadways (freeways and arterials). The study found that shifted exponential distribution and gamma distribution appear to reasonably fit data from freeways and atrerials, respectively.

COMPARING INTERNATIONAL CRASH STATISTICS

In order to examine national developments in traffic safety, crash statistics from several of the more developed countries are compared with those of the United States. Data obtained from the Fatality Analysis Reporting System (FARS) and the International Road Traffic and Accident Database (IRTAD) are analyzed. Trend analysis for the countries included, the United States, the European Community, Canada, Japan, New Zealand, and Australia, show that all regions have experienced decreases over time in the fatality rate per 100,000 population as well as the fatality rate per 100,000 registered vehicles. Fatality data are partitioned by age group, travel type, and roadway type. A variety of problems in collecting and analyzing international data is presented with some recommendations for further improvement.

Reversing Direction of Transportation Planning Process

The process of transportation planning begins with an assumed land use and then projects future traffic volumes. To determine land-use limitations as a function of the capacity of the transportation system, we reversed the direction of the planning process, beginning with transportation system characteristics as the independent variable and employment and population as dependent variables. We ultimately developed a direct estimation model. This technique directly estimates zonal trip ends based on transportation system variables that include link volumes, roadway types, travel distances, and the geographical position of the zone. Additionally, we regressed retail employment, nonretail employment, and population to zonal trip ends. We calibrated this model for the 1967 base year in the Charlottesville, Va. area and then applied it for the 1979 forecast year. We then used lessons learned to calibrate the model for the 1979 base year (a training set of data) and apply it for the 1990 forecast year (a test se...

The prevalence of non-standard helmet use and head injuries among motorcycle riders

Objectives: This study examined the prevalence of non-standard helmet use among motorcycle riders following introduction of a mandatory helmet use law and the prevalence of head injuries among a sample of non-standard helmet users involved in motorcycle crashes. Methods: Motorcycle rider observations were conducted at 29 statewide locations in the 2 years following the introduction of the mandatory helmet use law in January, 1992. Medical records of motorcyclists who were injured in 1992 for whom a crash report was available and for whom medical care was administered in one of 28 hospitals were reviewed. Chi-squares and analysis of variance were used to describe differences between groups. Results: Prevalence of non-standard helmet use averaged 10.2%, with a range across observation sites from 0 to 48.0%. Non-standard helmet use varied by type of roadway, day of week, and time of day. Injuries to the head were more frequent and of greater severity among those wearing non-standard helmets than both those wearing no helmet and those wearing standard helmets. Conclusions: Non-standard helmets appear to offer little head protection during a crash. Future study is needed to understand the dynamics leading to head injury when different types of helmets are worn.

Evaluation of the On-Road Behavior of 16-ft-Wide Mobile Homes in North Carolina

The overall objective of this effort was to evaluate the operational behavior and effect on surrounding traffic of 16-ft (4.9-m) wide mobile homes on various types of roadways and compare the results with similar measures for 14-ft (4.3-m) wide units. The evaluation was accomplished by following a sample of 16-ft and 14-ft units on Interstates, other multilane highways, and two-lane roads and videotaping the positions of the vehicles in relation to the roadway and to oncoming and overtaking vehicles. In addition, standardized measures were made for a sample of individual images from the videotapes, and the resulting data were analyzed to determine differences in operations between 14-ft- and 16-ft-wide units as well as differences in the effects on other traffic. Measures examined included lane positioning of the mobile homes and surrounding traffic and shoulder encroachments by both the mobile homes and other traffic. Encroachments of oncoming or overtaking vehicles on the shoulder show significant differences between the two sizes of mobile homes. Where lane or shoulder widths are narrow, the oncoming or overtaking vehicles used the shoulder to get by or around the 16-ft units more often than when they encountered the 14-ft units. The results produced recommended pavement widths for the two sizes of mobile homes. For 14-ft units, the amount of paved surface required is 4.9 m (16 ft). For 16-ft-wide units, the required amount of paved surface is 5.2 m (17 ft).

Evaluation of Speed Limits in Kentucky

The objectives were to examine current criteria and procedures used for setting speed limits and to determine appropriate speed limits for various types of roads. The study involved a review of literature, collection and analysis of speed data, and collection and analysis of accident data. The speed data included moving speed data on various highway types and a comparison of speed data before and after speed limit changes. Accident data were collected at locations where speed limits were changed and also on sections of adjacent Interstates with different speed limits. The speed data indicate that a large percentage of vehicle speeds exceed posted speed limits, with the highest percentage being on urban Interstates and two-lane parkways. The speeds for trucks were slightly lower than for cars. A comparison of speed data at locations where speed limits were changed showed only slight differences. A comparison of accident rates at adjacent sections of Interstate where the speed limit was 88.6 km/hr (55 mph) and 104.7 km/hr (65 mph) did not find a substantial difference in the total, injury, or fatal accident rates. Except where legislatively mandated speed limits apply, the 85th-percentile speed should be used to establish speed limits. Maximum limits are given for various types of roadways. Different speed limits for cars and trucks are recommended for some roadways. An engineering study must be conducted before the speed limit should be changed for any specific section of roadway.

Road Traffic Violations and Seat Belt Use in Kuwait: Study of Driver Behavior in Motion

Despite heavy investments in the transportation infrastructure and the existence of a young vehicle fleet, road safety in the affluent State of Kuwait continues to decline. Poor driver behavior and lack of enforcement of traffic regulations are believed to be the main causes of the unsafe driving environment. The findings of a research project designed to examine the relationship between seat belt use and road traffic violations in Kuwait are reported. The traffic violation behavior of 821 randomly selected drivers was recorded while the drivers were followed to their destinations. Factors of nationality, age range, gender, roadway type, vehicle type, time of day, trip time, and trip distance were also monitored. The average sample nonuser of seat belts made more than twice as many violations both per kilometer of travel and per minute of trip time than did seat belt users. Seat belt nonusers and young drivers (especially Kuwaitis) were found to be overrepresented in the violating groups, and discriminant analysis successfully discriminated between the high and low violators of traffic rules.

Effectiveness of Automated Speed-Monitoring Cameras in Kuwait

In 1994 the General Traffic Department installed automatic radar cameras to monitor traffic speed at a number of strategic roadway locations in Kuwait. The aim was to lower the number of high-speed violations and thus reduce road accidents. Recent traffic safety records point to an increase in both the number of violations and the occurrence of road accidents. It is argued in this paper that without live enforcement support and active follow-up of camera-recorded violations, the effectiveness of these cameras in improving road safety is insignificant at best, particularly in the undisciplined driving environment of the oil-rich nations in the Middle East. The speed of traffic was simultaneously measured via radar instruments both at the automatic camera site and at sections approximately 1 km before or after or before and after the cameras at eight camera locations. Measurements were recorded for six 1/2-hr periods at each site for a total of 72 hr over a period of 3 months, so that morning, afternoon, and after-dark hours, as well as different days of the week and roadway types, were covered. Analysis of the speed data showed that for the three daily periods and various roadway types, traffic speeds were consistently higher in sections before or after or before and after the automatic camera at the camera site. Statistical tests indicated that the difference in speed measured at and away from the cameras was at the 99 percent level. The findings demonstrate that in a traffic environment characterized by poor driving behavior, inconsistent and piecemeal driver education programs, and insufficient presence of law enforcement officials, reliance on automatic cameras alone to reduce traffic violations is doomed to fail.

Evaluation of Shared-Use Facilities for Bicycles and Motor Vehicles

This study was conducted for the Florida Department of Transportation with an objective of evaluating the safety and utility of shared-use facilities to provide engineers and planners comprehensive results that can be used in planning, designing, and constructing roadways to be shared by motorists and bicyclists. The results were developed from an analysis of observations of bicyclists and motorists interacting on different types of roadways. The evaluation included roadways with wide curb lanes, bicycle lanes, and paved shoulders. Locations from both rural and urban environments were included and varied in terms of motor-vehicle speed, traffic volume, lane width, and number of lanes. The operational measures of effectiveness used in evaluating the different types of facilities included ( a) lateral placement of the bicyclist, ( b) lateral placement of the motor vehicle, ( c) separation distance between the bicycle and the motor vehicle, and ( d) encroachments by the motorist or bicyclist during the passing maneuver. Results of the analysis showed that the type of facility (wide curb lane versus bicycle lane versus paved shoulder) does have a significant effect on the separation distance between bicyclists and motor vehicles; this distance ranged from 1.80 to 1.95 m (5.9 to 6.4 ft). The findings also indicated that paved shoulders and bicycle lanes generally result in similar interactions between motorists and bicyclists and that when compared with wide curb lanes they offer some distinct advantages to both user groups. The results also indicated that bicycle lanes as narrow as 0.92 m (3 ft) provide sufficient space for motorists and bicyclists to interact safely. At the same time, a 1.22-m (4-ft) wide bicycle lane tended to optimize operating conditions because there were very few differences in the measures of effectiveness when 1.22-m lanes were compared with wider lanes.

Developing a Travel Time Congestion Index

A congestion index that is keyed to the differences in actual versus desired travel times for various types of roadways is described. The suggested index provides a continuous scale for assessing the amount of congestion incurred. It encompasses a wide range of values and is easy to understand and use.

Developing a Travel Time Congestion Index

A congestion index that is keyed to the differences in actual versus desired travel times for various types of roadways is described. The suggested index provides a continuous scale for assessing the amount of congestion incurred. It encompasses a wide range of values and is easy to understand and use.

A Conjoint Analysis of Five Factors Influencing Heavy Vehicle Drivers Perceptions of Workload

Conjoint analysis, a multi-factor subjective scaling technique, was used in a study of heavy vehicle drivers to obtain a measure of their perceived workload demands under different driving conditions. These included combinations of low and high levels of traffic density, lighting, roadway type, visibility, and traction. A tradeoff comparison analysis was used to collect the conjoint scaling data from a subset of the complete 2−2−2−2−2 design. Results indicated that an additive factor representation fit the data very well, but that the five factors had very different importance weights. The drivers’ orderings of perceived demand appeared to be inversely related to their control over the conditions. The two most important factors (traction and visibility) are effectively environmental factors that cannot be easily controlled by the driver. The other three factors (traffic density, highway type, and lighting) can, at least to some extent, come under the control of the driver. Implications of these results and the use of conjoint scaling methodology are discussed.

Procedure for Developing Truck Accident and Release Rates for Hazmat Routing

To conduct risk assessments in routing studies for the highway transportation of hazardous materials (hazmat), estimates of accident and release rates are essential. Published literature underscores the importance of these rates in risk assessment, and the significant shortcomings of the available data. Truck accident rates are developed in this paper as a function of roadway type and area type (urban/rural) from state data on highway geometrics, traffic volume, and accidents. Release probabilities in accidents are derived from a combination of federal and state truck accident data bases. The procedure is presented in detail. A discussion of the dangers of combining data from different states is also presented, along with justification for the decision of the writers to do so. A revised model for the accident probability portion of the U.S. Department of Transportation (DOT) hazardous materials routing guidelines is recommended. Statistical tests are presented to determine whether accident rates based on site-specific data or systemwide values, such as those derived in this paper, should be used for any particular route segment. Language: en

Attentional demand requirements of an automobile moving-map navigation system

The objective of this research was to assess the driver visual attentional demand requirements of an operational in-car navigation system. Thirty-two driver subjects ranging in age from 18 to 73 drove a specially instrumented vehicle on various types of public roadways with varying traffic conditions. Drivers performed both specific navigation system tasks and conventional tasks using dashboard instrumentation. Comparisons were then made between the two types of tasks. Results show that the demand of most of the navigation tasks was comparable to that of one or more conventional tasks. Modifying the remaining navigation tasks to make information more readily available would reduce their demand.

Indirect wetland drainage in association with Federal highway projects in the Prairie Pothole Region

Wetland losses associated with Federal-aid-interstate, primary, and secondary highways were documented in the Prairie Pothole Region of North Dakota, South Dakota, and Minnesota in the Spring of 1986. Data on indirect wetland loss were collected using a fixed-wing aircraft and were stratified by state, physiographic region, and type of highway. We recorded 734 wetland basins totaling 574.3 ha being drained via open ditches or subsurface tiles into rights-of-way along 3,503 km of roadway. Total estimated loss in the tristate area was at least 11,243 ha along 56,737 km of roadway constructed using Federal monies. No differences (P<0.05) in drainage rates (ha per km of roadway) were detected when states, physiographic regions, or roadway types were compared. No differences (P<0.05) were found between newly reconstructed and existing older roadways. Recommendations as a result of this study include the assessment and documentation of potentially illegal drains into the rights-of-way of Federal aid highways to enforce current wetland protection efforts. Another recommendation calls for the establishment of a “highway-impact-area” in which a zone of wetland loss could be delineated and monitored. This information can potentially be used for mitigation efforts and for a more informed approach to the planning process of future Federal-aid highway projects.

Nonverbal Communication Between Motor Vehicle Drivers: Waves in Kansas

Variables related to responsive or spontaneous waving behaviors of male and female automobile drivers were investigated. Variables associated with waving included the sex of the respondents and their passengers, number of passengers, and vehicle and roadway types. Observed differences in the frequency of waving were tentatively interpreted as indicative of prevailing sex roles.

Canadian department of transport national driving survey 1978–1979

For comparison with regularly-available road accident data, the Department's Road Safety Branch attempted to obtain aggregate exposure measures in its National Driving Survey of 1978–1979. Distance travelled and travel time were the major target variables, to be classified by age, sex and experience of drivers, model year and type of vehicles, roadway type and surface condition, and time of day, week and month. Attempts were also made to simultaneously obtain data on alcohol use and vehicle fuel consumption. The method chosen was to sample drivers by geographic area and by month for one year, obtaining from each respondent a seven-day log of trips driven in vehicles under 10,000 lb gross weight. The logs included odometer readings to reveal trip distances. Two personal interviews were conducted with each respondent: first to obtain background data on drivers and vehicles, and introduce the trip “diary”; and subsequently to review the diary for accuracy. A pilot survey revealed that drivers could be persuaded to provide complete trip records, but that the survey methods did not produce accurate data on exposure by class of road, nor reliable data on either alcohol use or fuel consumption. The main survey took place from May 1978 to June 1979, obtaining usable responses from almost 10,000 drivers on approximately 200,000 trips. Response rates to different stages of the sampling and survey procedure are presented, the most significant being that 62% of drivers provided apparently-complete diaries. A follow-up investigation of non-respondents produced some success, and some reassurance about non-response bias.