Scheduled time interval between two vehicles operating in the same direction on a transit route; may vary over the course of a day or week, with changes in rider demand.

An arc passing between two electrodes in a pressurized tube causes metallic additives to vaporize and produce light; HID lamps have a longer life and provide more lumens (light) per watt than many other light sources; available in mercury vapor, metal halide, and high/low pressure sodium.

High Occupancy Vehicle - A passenger vehicle carrying two or more persons; HOV lanes typically require a minimum number of occupants or charge a fee for a vehicle to use facilities.

Describes an area designed to allow pedestrians to comfortably walk from one location to another and interact with the built environment; an effort to create an appropriate relationship between human beings and the size/function of surrounding buildings; an emphasis on building features and characteristics which can be observed in close proximity, at the speed a pedestrian would travel.

The cyclical movement of water between the earth and the atmosphere through precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transpiration.