MODELLING MAINTENANCE INTERVALS AND ROADSIDE SERVICE FACILITY SPACING FOR INTERNATIONAL ROAD TRAINS ON THE TRANSIT CORRIDORS OF UZBEKISTAN

International road trains operating on the transit corridors of Uzbekistan cover 3–7 thousand km per trip and pass through segments of different road categories, mountain passes, settlements, border crossings and climatic zones. The current normative approach assigns a single operating-condition category to a vehicle and therefore either overstates or understates the required frequency of maintenance. This paper develops a theoretical framework for the technical service of such vehicles. First, a complex coefficient of transit operating conditions Ktr is proposed as the product of length-weighted coefficients of road category and climate and an idle-time coefficient that converts engine operation at border queues into equivalent mileage. Second, the maintenance interval is made a multiple of the round-trip length so that scheduled maintenance always falls between trips at the carrier’s base, and the semi-trailer interval is synchronised with that of the tractor. Third, the interval of individual elements is chosen as the smaller of a reliability-based limit (Weibull model) and a cost-optimal value that accounts for the high cost of a failure on the road. Fourth, the spacing of roadside service facilities is derived from the driving-time rules of the AETR and from the failure-flow parameter. For the Andijan – Ivanovo route (round trip 7 230 km) Ktr = 0.850, which gives maintenance every 7 trips (50 610 km) for a 60 000 km base interval. For the measured corridor speed of 46.1 km/h, the distance between full-service “Service area” facilities must not exceed 207 km, with about 100 km recommended. Microsimulation in PTV Vissim shows that a 150 m parking lane adjoining the carriageway reduces flow speed by 38.7 % on two-lane and 49 % on three-lane roads once traffic volume exceeds 1 500 and 3 000 veh/h, respectively.