Synthesis of highway practice ;

The performance of CRCP has revealed a number of failure modes that are traceable to design, construction, materials, and maintenance deficiencies and such other factors as environemntal conditions and traffic loadings. This report of the Transportation Research Board includes a review of the cumulative experiences of state that have constructed and maintained CRCP. Guidelines for repair techniques are included, and areas of needed research are identified.

Changeable message signs are being used increasingly to reduce congestion and prevent accidents in both rural and urban locations. Because of the rapid development of improved technology, there is a need for up-to-date information on the characteristics, applications, and effectiveness of changeable message signs. This report of the Transportation Research Board includes information on requirements for design, installation, operation, and message effectiveness. It also contains a review of previous and current research, and future development needs are identified.

The increasing complexity of operating highway and transportation departments has caused many agencies develop comprehensive computer systems for storage and retrieval of data. This report of the Transportation Research Board reviews and evaluates what has been accomplished to data and includes recommendations for future development.

Expenditures for maintenance are not keeping pace with the needs of the nations highways. Desirable maintenance activity is not being carried out, and the backlog of work needed to restore the facility to good condition is growing. Difficult judgments must be made in deciding to defer maintenance. To effectively manage a maintenance program, levels of service must be able to be defined, measured, and evaluated. This report of the Transportation Research Board reviews concepts for quantifying maintenance needs, setting priorities, and developing strategies. Relevant studies in progress are discussed and additional research needs are outlined.

Design principles and procedures and maintenance practices for bridge drainage systems are evaluated in this report, which also includes recommendations for improvements on current practice. Bridges should have adequate cross-slope and grade to allow the water to run quickly into drains. Where grades permit, some states carry all the water to catch basins at the ends. An inlet box may be used to collect the runoff. Some states have detailed procedures for determining drain spacing. Debris can be controlled by keeping it out of inlet boxes, accepting and storing it so it cannot go through the system, or transporting it through. Maintenance at regular intervals is the key to the success of a drainage system. Disposal of run off water can be a simple straight drop onto the land or water beneath the bridge or a pipe system to carry the water to the local sewer system. Current practices indicate that deck cross-slope and grade should be less than 2% and 0.5% respectively; that bridge drains may be holes through the deck, fabricated inlet boxes, or catch basins at the ends of the bridge; that inlet areas should be as large as possible; that pipes should have a minimum diameter of 6 in., a miminum radius of 18 in., and a minimum slope of 2%; that cleanout plugs and elbows should be easily accessible; that there should be improved communication between designers and maintenance personnel; and most importantly, that bridge drainage systems should be regularly and carefully inspected and serviced.

The procedures followed in programming (the matching of available projects with available funds to accomplish the goals of a given project) are outlined. The 15-step basic programming process, derived from a review of published documents and interviews with highway administrators, ranges from project initiation through modification. Several steps (e.g. prioritizing and financial analysis) are described in detail, and a list of definitions for the basic terms used in planning and programming is provided.

In recent years, apparent changes have evolved in the physical properties of asphalt cements used in pavement construction. Some of these properties are not controlled or are controlled only partially by AASHTO specifications. This report of the Transportation Research Board reviews all available information relating durability and performance of asphaltic concrete mixtures to the properties of the asphalt cement. Recommendations for improved test procedures and criteria are included. The report concludes that hardness of the asphalt is the property most important to pavement performance.