This report is an Informational Guide for highway agencies on the use of low-cost improvements to alleviate operational problems on two-lane highways. The Guide addresses both passing and turning improvements that can be constructed for a lower cost than construction of a continuous four-lane highway. The passing improvements presented in the Guide include passing lanes, climbing lanes, short four-lane sections, turnouts, shoulder driving, and shoulder use sections. The turning improvements included are intersection turn lanes, shoulder bypass lanes, and two-way leftturn lanes. Design and traffic control guidelines presented for these improvements include location and configuration guidelines, geometric design criteria, recommended signing and marking practices, and operational and safety effectiveness estimates. Guidelines for planning operational improvements over an extended section of two-lane highway are provided. The Guide also reviews evaluation procedures for passing and turning improvements, with particular emphasis on the application of the 1985 Highway Capacity Manual procedures for two-lane highways. A case study involving the evaluation of passing lane effectiveness on two-lane highways is also presented. (Author/publisher)
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