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Author: Publisher: ISBN: Category : Roads Languages : en Pages : 89
Book Description
"To compare the safety effects of a uniform speed limit (USL) for all vehicles as opposed to a differential speed limit (DSL) for cars and heavy trucks, detailed crash data, speed monitoring data, and traffic volumes were sought for rural interstate highways in 17 States for the period 1991 to 2000. Conventional statistical tests (analysis of variance, Tukey's test, and Dunnett's test) were used to study speed and crash rate changes in the four policy groups. A modified empirical Bayes formation was used to evaluate crash frequency changes without presuming a constant relationship between crashes and traffic volume"--Technical report documentation page.
Author: Publisher: ISBN: Category : Roads Languages : en Pages : 89
Book Description
"To compare the safety effects of a uniform speed limit (USL) for all vehicles as opposed to a differential speed limit (DSL) for cars and heavy trucks, detailed crash data, speed monitoring data, and traffic volumes were sought for rural interstate highways in 17 States for the period 1991 to 2000. Conventional statistical tests (analysis of variance, Tukey's test, and Dunnett's test) were used to study speed and crash rate changes in the four policy groups. A modified empirical Bayes formation was used to evaluate crash frequency changes without presuming a constant relationship between crashes and traffic volume"--Technical report documentation page.
Author: David L. Harkey Publisher: ISBN: Category : Speed limits Languages : en Pages : 78
Book Description
The objectives of this study were to determine whether differential or uniform speed limits are more beneficial to transportation safety and traffic operations on Interstate highways. The approach to achieving this objective was to examine speed and accident data from States employing both types of limits. Speed data were collected in 12 States at rural and urban locations representing all speed limits currently established on the Interstate highway system for cars/trucks, i.e., 55/55 mi/h (89/89 km/h), 65/55 mi/h (105/89 km/h), 65/60 mi/h (105/97 km/h), and 65/65 mi/h (105/105 km/h). Accident data were obtained from nine States which were geographically distributed across the country and representative of all rural Interstate speed limits currently established. For the speed data collected, a number of measures of effectiveness (MOEs) were examined including mean speed, speed variance, compliance, and speed distribution measures. For the accident data collected, types of crashes were examined (e.g., rear-end) along with vehicle type involvement (e.g., car-into-truck) and crash severity. This final report summarizes the effects of uniform and differential speed limits on transportation safety and traffic operations as determined by the examination of speed and accident data.
Author: Jack D. Jernigan Publisher: ISBN: Category : Speed limits Languages : en Pages : 52
Book Description
In 1987, the Secretary of Transportation and Public Safety created a task force to study the potential effects of raising the speed limit on rural interstate highways in Virginia. In its 1988 session, the Virginia General Assembly passed legislation to increase the speed limit on rural interstate highways to 65 mph for passenger vehicles, but the 55 mph limit was retained for buses and large trucks. After implementation of the higher speed limit on July 1, 1988, the Secretary reconvened the task force to design a study to determine the effects of the changed speed limit. The Virginia Transportation Research Council was again asked to serve a the staff for the task force. The preliminary data provided in this report represent only 5 months of experience with the 65 mph speed limit and are presented for information only. Any conclusions drawn from these data would be inappropriate and perhaps incorrect. After the speed limit for cars was increased by 10 mph, the average and 85th percentile speeds traveled by all vehicles on the rural interstate system increased by 3 mph, to 63 mph and 68 mph, respectively. The average and 85th percentile speeds traveled by trucks and buses, for which the speed limit remained at 55 mph, decreased slightly. Between July 1 and November 30, 1988, there were 44 fatalities in 35 fatal crashes on rural interstate highways in Virginia. This was a 76 percent increase over the 25 fatalities and a 52 percent increase over the 23 fatal crashes for the same time period in 1987. In the states that increased the speed limit, there was a 41 percent increase overall in the number of fatalities, but in states that did not increase the speed limit, there was a 54 percent increase in fatalities--higher than that noted for states that increased the speed limit. Many of the crashes that accounted for the increase in the number of fatal crashes on rural interstate highways occurred on I-81, and all of the multiple-fatality crashes occurred on either I-81 or I-95. In comparison with 1987, the number of fatal crashes in 1988 included 5 more involving vehicles that ran off the road, 4 more involving tractor trailers, and 3 more involving pedestrians. In October 1988, there was an abnormally high number of fatal crashes and fatalities on Virginia's rural interstate highways, but no patterns were found to explain this 1-month abnormality. Because there are not sufficient data to determine the reasons for the increases in fatal crashes and fatalities, data will be gathered over a 5- year period to determine the effect of the changed speed limit on Virginia's rural interstate highways.
Author: Jack D. Jernigan Publisher: ISBN: Category : Interstate Highway System Languages : en Pages : 158
Book Description
In April of 1987, Congress passed the Surface Transportation and Uniform Relocation Assistance Act of 1987, which allows the states to raise, without penalty, the speed limit on interstate highways outside of urbanized areas with a population of 50,000 or more. This study estimated that an increase in the rural interstate speed limit in Virginia would have both positive and negative outcomes.-The average speed traveled on the rural interstate highway system has already increased by 3.6 mph in Virginia; this is comparable to that experienced in states that have raised the speed limit. However, if the speed limit on the rural interstate highway system is raised from 55 mph to 65 mph, it is estimated that in the short run the average speed traveled on the rural interstate will increase by an additional 3 mph, from 60 mph to 63 mph. Increased speeds would be expected to result in increased stopping distances and an annual increase of between 6 and 18 fatalities and between 171 and 405 injuries. Further, injuries would likely be more severe as a result of the higher speeds traveled. If the average speed continues to increase in the long run, or if higher speeds spill over onto the urban interstate highway system or rural collector roads, then additional injuries and fatalities would be expected on those systems as well. On the other hand, the primary quantifiable benefit of the higher limit would be a savings of 1.3 million hours in business and commercial travel time. This study has also found that almost 60% of the Virginians surveyed would prefer a 65 mph speed limit to a 55 mph limit on the rural interstate highway system. Finally, because of the current speeds, the geometric design, and the accident history of the rural interstates in general, it would be possible to raise the speed limit without violating traffic engineering tenets for setting speed limits. However, if the speed limit is raised, establishing a truck speed limit differential below the limit established for passenger cars would promote increased speed variance between cars and trucks, thereby creating a more dangerous environment than if the speed limit were raised to the same level for both cars and trucks.
Author: Haggai Davis Publisher: ISBN: Category : TRANSPORTATION Languages : en Pages : 0
Book Description
"The National Highway Traffic Safety Administration (NHTSA) reported that 37,461 people died in 2016 on US roads, marking the second year in a row that the number has increased [1]. Many transportation-related agencies have adopted a “Vision Zero” or “Towards Zero Deaths” campaign aiming to eliminate the need for that statistic. Speed can often play a role in fatalities, so setting the proper speed limit for roadways is important in saving lives. American speed limits have a complicated history over the past 50 years, which hinders researchers’ ability to look at much longer stretches of data and draw conclusions about determining the best speed limit strategy. From 1973 to 1987, the maximum speed limit was 55 MPH. After that, Congress raised the allowable limit to 65 MPH. It was not until 1995 that states had full discretion over setting an appropriate limit. Some states raised the speed limit for all vehicles equally – a uniform speed limit (USL). Others raised speeds for trucks less than that of cars – a differential speed limit (DSL). On the surface, the benefit of a DSL seems intuitive, lowering the speeds for big trucks would reduce the severity of accidents. However, it also has the effect of increasing total variance in speed which increases the number of accidents. This report aims to explore the literature published about these issues and to inform decision makers about the factors to be weighed when considering DSL versus USL. It was prepared in response to a request in the 2017 session of the Louisiana House of Representatives where the Louisiana Department of Transportation and Development (DOTD) was asked to “study the safety and operational impacts of differential speed limits on interstate highways” (House Concurrent Resolution 112). Thus, the purpose of this study is to inform the Louisiana Legislature about the documented benefits and costs of a differential speed limit for passenger cars versus larger vehicles specifically with regards to the topics of Safety, Mobility and Operations, Fuel Consumption and Emissions, and Truck Determination as outlined in HCR 112."--Introduction.
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Author: David L. Harkey
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Author: United States. National Highway Traffic Safety Administration
Author: Jack D. Jernigan
Author: Jack D. Jernigan
Author: Haggai Davis
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