| High-Occupancy Toll (HOT) Lanes

High Occupancy Toll (HOT) Lane Study to Ease Traffic Congestion Low Level Aerial Photography Eliminates Traffic Hazards for Surveyors AERO-METRIC Dulles Division was retained by HNTB for a two phase project. For Phase I, 1"= 50', two foot contour mapping was provided for a 1,200 foot band along a 14-mile segment of the I-495 Washington, D.C. Beltway. In Phase II: Aerial photo-graphy was obtained using a helicopter-mounted camera. Control point elevations were determined by differential spirit leveling to a relative accuracy of 0.01 feet.

Elevations were determined at interchange areas, bridge crossings, drainage inlets, and at the tops and along the flow lines of barrier walls. The predicted accuracy of these elevations is +/-0.05 feet with respect to the project vertical datum. "The accuracy and reliability of the mapping data provided by Air Survey has always been consistent with the requirements of HNTB and VDOT. This project was no exception. High accuracy photogrammetric elevations to ground survey tolerances, on paved surfaces, avoided traffic disruptions and improved the safety factor. This increased the likelihood of meeting design-phase project milestones." —Robert B. Newman, P.E., V.P, HNTB

BACK TO PROJECTS