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Evaluating the Relevance of 40 MPH Posted Minimum Speed Limit on Rural Interstate Freeways

Title: Evaluating the Relevance of 40 MPH Posted Minimum Speed Limit on Rural Interstate Freeways.
Name(s): Muchuruza, Victor, author
Mussa, Renatus N., professor directing thesis
Sobanjo, John O., committee member
Ping, W. Virgil, committee member
Department of Civil and Environmental Engineering, degree granting department
Florida State University, degree granting institution
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2003
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: The practice of posting minimum speed limits on rural Interstate freeways is predicated on the desire to reduce vehicle conflicts caused by speed variability in a traffic stream. In some states, minimum speed limit signs are posted on rural interstate freeways and other limited access facilities. However, the relevance of the 40 MPH minimum speed limit posted on Florida Interstate freeways system is increasingly being questioned in light of the increase of maximum speed limit to 70 MPH following the National Highway System (NHS) Designation Act of 1995 which repealed the federally sanctioned maximum speed limit. This study was aimed at evaluating the operational and safety characteristics of Florida Interstate freeways with 40 MPH minimum speed sign. Speed and crash data were collected on four major Interstate freeways in Florida. The speed data revealed that the 15th percentile speed on all sites is 60 mph or above on both four-lane and six-lane freeways sections. The average speeds on all sites were approximately five standard deviations above the 40 mph speed value. The coefficients of variation ranged from 7 to 11 percent while the trimmed variance analysis showed that vehicles traveling below 55 mph had insignificant contribution to the variation of traffic speeds. Comparison of speed data collected prior to raising the speed limit from 65 mph to 70 mph showed that the average speeds increased by 5 mph while the variances did not change significantly. However, the coefficients of variation have increased significantly. The analysis of safety experience on these freeway sections revealed that speed variation is potentially a contributing factor to the majority of the crashes analyzed. Stratification of crash involved vehicles by speed showed that vehicles traveling with speeds below 40 MPH were overrepresented. The research further discusses safety modeling using Poisson regression.
Identifier: FSU_migr_etd-2211 (IID)
Submitted Note: A Thesis Submitted to the Department of Civil Engineering in Partial Fulfillment of the Requirements for the Degree of Master of Science.
Degree Awarded: Fall Semester, 2003.
Date of Defense: November 17, 2003.
Keywords: Minimum Speed Limit, 15th Percentile Speed, Speed Variability
Bibliography Note: Includes bibliographical references.
Advisory Committee: Renatus N. Mussa, Professor Directing Thesis; John O. Sobanjo, Committee Member; W. Virgil Ping, Committee Member.
Subject(s): Civil engineering
Environmental engineering
Persistent Link to This Record:
Owner Institution: FSU

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Muchuruza, V. (2003). Evaluating the Relevance of 40 MPH Posted Minimum Speed Limit on Rural Interstate Freeways. Retrieved from