Horizontal curves are a common and essential element of the rural highway system, and it is essential to sign and mark them consistently to minimize curve crash risk. Curve signing and marking consists primarily of conducting an engineering study to set the curve advisory speed, posting the advisory speed if necessary, and providing other signs and markings (such as Chevrons) based on the curve severity. Additionally, curve safety can be addressed through more significant treatments such as installing a pavement friction treatment or even straightening the curve if the highway can be realigned.
Over the past decade, the Texas Department of Transportation has sponsored several research projects to (1) develop new procedures for setting curve advisory speeds on rural two-lane highways, (2) examine crash frequency on rural highways in general, (3) identify conditions when pavement friction treatments are beneficial and cost-effective, and (4) extend curve advisory speed study methods to four-lane rural highways. This Handbook provides engineers and technicians with a consolidated source for applying all the preceding analysis tools to assess curve safety and implement needed treatments.
This report is available online at https://static.tti.tamu.edu/tti.tamu.edu/documents/0-6960-P1.pdf