Access Control Design On Highway Interchanges
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Access Control Design on Highway Interchanges
The adequate spacing and design of access to crossroads in the vicinity of freeway ramps are critical to the safety and traffic operations of both the freeway and the crossroad. The research presented in this report develops a methodology to evaluate the safety impact of different access road spacing standards. The results clearly demonstrate the shortcomings of the AASHTO standards and the benefits of enhancing them. The models developed as part of this research were used to compute the crash rate associated with alternative section spacing. The study demonstrates that the models satisfied the statistical requirements and provide reasonable crash estimates. The results demonstrate an eight-fold decrease in the crash rate when the access road spacing increases from 0 to 300 m. An increase in the minimum spacing from 90 m (300 ft) to 180 m (600 ft) results in a 50 percent reduction in the crash rate. The models were used to develop lookup tables that quantify the impact of access road spacing on the expected number of crashes per unit distance. The tables demonstrate a decrease in the crash rate as the access road spacing increases. An attempt was made to quantify the safety cost of alternative access road spacing using a weighted average crash cost. The weighted average crash cost was computed considering that 0.6, 34.8, and 64.6 percent of the crashes were fatal, injury, and property damage crashes, respectively. These proportions were generated from the field observed data. The cost of each of these crashes was provided by VDOT as $3,760,000, $48,200, and $6,500 for fatal, injury, and property damage crashes, respectively. This provided an average weighted crash cost of $43,533. This average cost was multiplied by the number of crashes per mile to compute the cost associated with different access spacing scenarios. These costs can assist policy makers in quantifying the trade-offs of different access management regulations.
Access Management on Crossroads in the Vicinity of Interchanges
Author: Marc A. Butorac
language: en
Publisher: Transportation Research Board
Release Date: 2004
TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 332: Access Management on Crossroads in the Vicinity of Interchanges examines current practices relating to access location and design on crossroads in the vicinity of interchanges. It identifies standards and strategies used on new interchanges and on the retrofit of existing interchanges.
Highway Noise; a Design Guide for Highway Engineers
Various methods of assessing noise, loudness, and noise annoyance are reviewed and explained; sources, types, and intensities of traffic noise are noted; typical means of abatement and attenuation are described; design criteria for various land uses ranging from low-density to industrial are suggested and compared with the results of previous BBN and British systems for predicting annoyance and complaint; and a design guide for predicting traffic noise, capable of being programmed for batch and on-line computer applications, is presented in form suitable for use as a working tool. A flow diagram describes the interrelationships of elements in the traffic noise prediction methodology, and each element is discussed in detail in the text. The text is presented of a tape recording that takes the listener through a series of traffic situations, with such variables as traffic distance, flow velocity, distance, outdoors and indoors, and presence or absence of absorbers and attenuators.