USE OF FREEWAY SHOULDERS TO INCREASE CAPACITY

The Texas State Department of Highways and Public Transportation approved for testing the concept of increasing roadway capacity on urban freeways by restriping the main-line pavement to create narrower lane widths and encroaching on the shoulder to create additional lanes for travel. Two sections of the US-59 Southwest Freeway in Houston were selected for study. The effectiveness of reconfiguring the main lanes was examined from the following aspects: operational characteristics of peak-period flow, driver acceptance of use of the shoulder lane, accident experience, benefit-cost analysis, and design and maintenance requirements. Expected improvements in operations during peak periods as a result of increased capacity were achieved. One section did not reach the anticipated level of improvement because of low driver use of the shoulder lane, and an analysis determined the need for a change in the length of that section. Accident experience was significantly reduced as a result of the modifications, and the benefit-cost analysis was extremely favorable to this type of low-cost improvement. The results of the study support the application of the use of shoulder and narrow freeway lanes for travel through bottleneck sections of urban freeways. /Author/