Criteria for High Design Speed Facilities (0-5544-1)

The Texas Department of Transportation (T xDOT) is embarking on a multi-decade effort to expand the state's transportation system. To accomplish this expansion, TxDOT has expressed an interest in using higher design speeds (above 80 mph U30 km/hl) to promote faster and more efficient travel within the state. Current state and national roadway design guidance does not provide criteria for design speeds above 80 mph [130 km/h], so design values are not available. The purpose of TxDOT Project 0 -5544, Development of High Speed Roadway Design Criteria and Evaluation of Roadside Safety Features, was to expand upon existing design speeds up to 100 mph [160 km/h]. Determination of preliminary criteria required extrapolation of existing equation as long with the use of engineering judgment. A Roundtable Discussion Group was assembled to obtain practicing engineers' opinions and views on the methodology used to determine the criteria and on the specific values of the criteria. The technical report developed as part of this project presents issues and concerns and shows potential values generated for design speeds of 85 to 100 mph [40 to 160k m/h] for: stopping sight distance, grades, vertical alignment, lane width, shoulder width, cross slope, horizontal alignment and superelevation, ramp design speed, ramp grades and profiles, ramp cross section and cross slope, distance between successive ramps, ramp lane and shoulder widths, ramp acceleration and deceleration lengths, roadside clear zones, median width, roadside slopes and diitches, crash testing, and roadside safety devices. The criteria developed in the project were provided to TxDOT. TxDOT incorporated project findings in the new TxDOT Roadway Design Manual Chapter8 : Mobility Conidor (5R) Design Criteria.