PAVEMENT DRAINAGE, WITH DISCUSSIONS AND CLOSURE

PAVEMENT DRAINAGE STRUCTURES DESIGNED FOR FOUR SPECIAL SITUATIONS ARE DESCRIBED ALONG WITH THE CONSIDERATIONS THAT WENT INTO THEIR DESIGN. CONCLUSIONS ARE BASED ON EXPERIENCE WITH STRUCTURES IN USE. PRESTRESSED CONCRETE GULLY GRATES FOR GRADES ARE ADVANTAGEOUS ON THE BASIS OF APPEARANCE, INITIAL COST, AND MAINTENANCE; EXCEPT IN SITUATIONS WHERE DEBRIS CLOGGING IS A PROBLEM, MORE COSTLY INSTALLATIONS ARE NOT JUSTIFIED. GULLY INLETS ON FREEWAYS MUST BE DESIGNED TO KEEP WATER OFF THE PAVEMENT AND TO ACCOMMODATE SHOOTING FLOW. THE SURFACE OF DRAINAGE STRUCTURES MUST BE DESIGNED FOR WAVE, RATHER THAN FLOWING WATER MOTION. THE USE OF MINIMUM SPECIFIC ENERGY AS A DESIGN CRITERIA IS A NEW AND PROMISING TECHNIQUE.