Improvement in Geometric Design of M1- M2 Interchange Islamabad

Abstract

Transportation engineering involves a variety of engineering and management skills, including planning, design construction, operational control, maintenance, and system optimization. The principal goal of the transportation engineer is to provide, operate and manage a safe system for urban and highway traffic. The Motorways of Pakistan are a network of multiple-lane, high-speed, limited or controlled-access highways, which are owned, maintained and operated federally by Pakistan's National Highway Authority (NHA). M-2 motorway is Pakistan's first motorway, the 357 km 6-lane, connecting the cities of Islamabad and Lahore and M-1 Motorway Pakistan's third motorway, the 155 km 6-lane, linking Peshawar with Islamabad. The current geometry and configuration of M-1/M-2 interchange is characterized by conflicting traffic maneuvers at two locations. First conflict is encountered between the Peshawar-bound traffic and Lahore-bound traffic from Islamabad as the exit facility diverges from the fast lane preceding a sharp turn and creates confusion. Second conflict is between the Peshawar-bound traffic entering M-1 and the Islamabad-bound traffic exiting from M-2. The existing geometry of the Interchange is a half clover-leaf which naturally causes the phenomena of weaving maneuvers. Also, minimum permissible distance between on-ramp and off-ramp facility is 600 meters according to AASHTO guidelines, while the provided distance here is 480 meters. This geometric inconsistency is likely to aggravate the problem with the increasing future traffic demand in the backdrop of developing China-Pakistan Economic Corridor where M-2 is part of its Eastern Route. Trumpet Interchange with loops in same quadrant are desirable because they eliminate the weaving problem. First conflict is resolved by providing a separate exit facility for Lahore-bound traffic on M-2 from Islamabad prior to the sharp turn. For second conflict a new loop is provided for Peshawar bound-traffic entering M-1 (on-ramp) over the existing loop used by Islamabad-bound traffic exiting from M-2. This project makes an endeavor to address these weaving maneuvers of traffic operations. AutoCAD Civil 3D® was employed to existing profile/ DEM data generated contours to develop the conflict free infrastructure design at the interchange. Two different infrastructure interventions were presented. Also, Volume counts data including both, turning and through movements at the interchange was used to simulate the traffic conditions of the existing and the proposed design using micro-level traffic simulation software VISSIM 8.0®. The proposed Infrastructure interventions are envisaged to improve the traffic operations on the vital highway Assets of Pakistan.