Directional Design-Hour Volume (DDHV) is the proportion of Annual Average Daily Traffic (AADT) in the peak-hour (design hour) in the predominant direction of traffic flow. DDHV is determined from field measurements on the facility under consideration or on parallel and similar facilities. It is given by multiplying AADT by K-factor and D-factor.
DDHV = AADT x K-factor x D-factor
DDHV is an important factor for accurately determining traffic capacity on highways and transportation networks. DDHV takes into account peak-hour volume fluctuation and directionality which is not captured in AADT (Annual Average Daily Traffic) or ADT (Average Daily Traffic).