Impacts of driveway right turns on urban arterial roadway operations

The maneuver of a vehicle turning right from an urban arterial into a driveway or unsignalized roadway results in delay to any through vehicle that is following this turning vehicle. This maneuver also causes a reduction of the capacity of the roadway. While the delay and capacity reduction caused by a single turn may be minimal, the repetition of this movement by many cars into multiple driveways along an urban arterial can result in substantial amounts of delay and reduction of capacity over time. Few researchers have attempted to quantify these variables, and the validity of their research has been limited by a lack of understanding of the right turn behavior, specifically, the deceleration pattern of a vehicle preparing to turn right. Twelve driveways adjacent to unban arterials in northwest Arkansas were selected for study, and the speeds of passenger cars turning right into these driveways were measured at various distances in advance of the driveway. This information was used to develop a model concerning the behavior of a motorist when preparing to execute a right turn maneuver. The model was used to estimate the delay and capacity reduction caused by a single right turning vehicle and to approximate the appropriate desirable length of a right turn deceleration lane.