Recommendations regarding higher axlemass limits for axles fitted with wide base tyres

Abstract

This paper presents the results of an investigation into possible higher axle mass limits for axles and axle units fitted with wide base tyres, i.e. tyres with nominal section widths of 385 mm, 425 mm and 445 mm, by comparing the road wear caused by single axles, tandem axle units and tridem axle units fitted with wide base tyres of various sizes and at different axle masses with the potential road wear caused by axles and axle units fitted with conventional single tyres and dual tyres loaded to the current permissible maximum masses. These comparisons are then used to arrive at recommended axle mass limits for axles and axle units fitted with wide base tyres, based on the principle of equal road wear. The road wear caused by the various axles fitted with the different size tyres are calculated in terms of Load Equivalency Factors (LEFs), which were calculated using the existing Mechanistic-Empirical Design Method (SAMDM) for flexible pavements through the application of the current mePADS software package. Based on the results of this study, axle and axle unit mass limits of 9 t for single axles, 18 t for tandem axle units and 24 t for tridem axle units are recommended for axles fitted with wide base tyres with a nominal section width of 425 mm or more.