Improvements in highway design methods and practices are reflected in this Third Edition of the handbook. The chapter on environmental issues has been updated throughout in view of ever-evolving regulations in that area. The chapter on highway design includes information from the latest AASHTO “Green Book.” The trend to replace bridges with spans up to about 60 ft (18 m) with stiffened special long-span corrugated steel and precast concrete drainage structures is documented in the chapter on culverts. The chapter on safety systems shows the trend to use median barriers over wider median widths than in the past. Metric units have been added throughout the text and in tables and figures wherever feasible.
The reader is cautioned that independent professional judgment must be exercised when information set forth in this handbook is applied. Anyone making use of this information assumes all liability arising from such use. Readers are encouraged to use the latest edition of referenced specifications and guides, because they provide more complete information and are subject to frequent change.
Roger L. Brockenbrough, P. E.
