Flexible Pavement Narrow Widening Best Practices and Lessons Learned

The Texas Department of Transportation (TxDOT) has experienced problems with construction quality and performance on narrow widening projects (i.e., projects that notch and widen pavement to increase lane width 2–8 ft or add a 2- to 5-ft shoulder). Texas has approximately 64,000 lane-miles of pavement with 9- to 11-ft wide lanes, which includes over 35,000 lane miles of Farm-to-Market (FM) roads (MapZapper 2011). In addition, approximately 20%, 26%, and 36% respectively of roadways with 9-, 10-, or 11-ft lanes have either no shoulder or a 1-ft shoulder. These roads are potential candidates for lane or shoulder widening to improve safety performance and increase capacity. However, due to constraints regarding construction equipment widths and other limitations, material selection options and compatibility, construction methods, and other issues, narrow widening projects can present construction and performance problems. These challenges include inadequate compaction of the subgrade, compaction of the base material at the notch-and-widen joint interface, drainage within the pavement and at the pavement surface, either high or depressed surface layer construction joints, and potential safety concerns. To effectively overcome these challenges, TxDOT has initiated this project to prepare a compendium of best practices and lessons learned regarding narrow widening projects.