Identifying, anticipating, and mitigating freight bottlenecks on Alabama interstates

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
University of Alabama Libraries

This project establishes a framework for the creation and maintenance of a statewide strategy for identifying, anticipating, and mitigating freight bottlenecks on interstate highways for the state of Alabama. It uses a methodology established and developed by Cambridge Systematics for identifying and quantifying bottlenecks. This research identified a total of nine freight bottlenecks on Alabama interstates using 2006 traffic data supplied by ALDOT. These include six bottlenecks, termed "capacity" bottlenecks, which are caused by an insufficient capacity in relation to demand (where the ratio of Average Annual Daily Traffic to the hourly capacity of the roadway in passenger cars per hour is greater than eight) on a basic section of roadway. The other three bottlenecks are "interchange" bottlenecks, which are similar to capacity bottlenecks except that they occur at interchanges involving multiple interstates. The six sections of roadway identified as capacity bottlenecks follow: * Interstate 65 from Exit 252 to Exit 259B * Interstate 65 from Exit 238 to Exit 246 * Interstate 20/59 from Exit 123 to Exit 130 * Interstate 65 from Exit 247 to Exit 250 * Interstate 10 from 26A to Exit 27 * Interstate 10 from Exit 15B to Exit 17A The three interchanges identified as bottlenecks follow: * Interstate 459 at Interstate 65 * Interstate 20/59 at Interstate 65 * Interstate 20/59 diverge (into separate Interstate 20 and Interstate 59) A third type of bottleneck called a "roadway geometry" bottleneck involves congested roadways that have grades greater than 4.5% lengths exceeding one mile. However, none of these types of bottlenecks were identified on Alabama interstates because there is no stretch of interstate of that length with that steep of grade. Identification of bottleneck locations was done using a GIS database that was created specifically for use in this report. This database merged multiple, previously existing databases including the National Highway Planning Network, the Highway Performance Monitoring System, and the Freight Analysis Framework. Each of the bottlenecks identified were assigned a cost value for the delay that it causes in 2006 as well as in 2025 and 2040. This type of information is useful to planners when they are selecting sections of interstate highways for upgrade. Similarly, projections of delay cost were calculated for interstate road sections and interchanges that were classified as bottlenecks in year 2006. For example, the George C. Wallace Tunnel in Mobile, which is the capacity bottleneck on Interstate 10 from Exit 26A to Exit 27, had roughly $150,000 in delay to freight movements in 2006 but is expected to increase to $1,836,000 in delay by the year 2025. That is a greater than ten-fold increase. The report also lists methods through which the basic framework established in this report can be improved upon to provide greater accuracy in bottleneck identification and delay cost calculations.

Electronic Thesis or Dissertation
Civil engineering, Transportation planning