Reconsidering Freeway Bottlenecks

Abstract

Implementing minor geometric and operational improvements on existing freeways to remove bottlenecks has the potential of achieving high benefits, yet it is not routinely done. Four case studies of bottleneck removal projects in Texas are presented in some detail with before-and-after evaluations of speeds, volumes, and crash histories. The case is made that many benefits may be realized for little cost. In addition, evaluations of nine other bottleneck removal projects are included in summary tables. Benefit–cost ratios as high as 400:1 have been found, with the lowest ratio being 9:1; costs ranged from $8,000 to $2.45 million. Injury crash rates were substantially lower after the bottleneck removal in almost all cases (average reduction of approximately 35%); however, an increase in crash rate was noted in one of the 13 cases.