A sufficient drainage on motorways is an important requirement for road safety. This could be problematic in superelevation transition sections, particularly in combination with wide carriageway width and low longitudinal gradients. High speeds lead to hydroplaning and cause accidents. The German 'Guidelines for the Design of Motorways' (RAA 2008) give recommendations, how to avoid zones with insufficient drainage. These are solutions that could be realized by road design, construction or traffic regulation including: - increase of the longitudinal gradient, - open-pored layer (porous asphalt), - constructional measures (gutter box), - avoidance of a superelevation transition by applying a negative cross slope with large radii, - special form of a transition (rolling crown), - speed limit at wet conditions. For the selection of appropriate measures, comprehensive information about their advantages and disadvantages are required. For that reason, a research project has been ordered to investigate and evaluate the different solutions regarding durability, dimension, construction and costs. Based on this, recommendations are given for selecting the best solution depending on local boundary conditions (number of lanes, asphalt or concrete, gradient). Considering construction and maintenance costs as well as accident costs, it is proved simultaneously, if it is an economic measure. As a result, there are recommendations for the guidelines for motorways. (Author/publisher)
Samenvatting