Development of a framework for determining minimum testing interval requirements for Network Level Skid Testing

As transportation agencies begin to shift the ownership and ultimate responsibility of their civil infrastructure assets such as highway networks and toll roads from the agency to the private sector, the importance of key performance indicators (KPI) such as level of safety are critical to ensure a high level of service. The safety of highway networks are usually assessed using various levels of service indicators such as ride quality (IRI), surface friction (SN), or number of collisions. In 2006, approximately 1,800 km of the provincial highway network was surveyed for friction data. This friction data was collected to determine a baseline of the current network friction levels in terms of a skid number. Testing was carried out at an interval of 1.0 km across the length of each highway segment. Network level friction testing can be characterized as expensive and time-consuming due to the complexity of the test and the traffic control requirements. As a result, any reduction in the required number of test points is a benefit to the transportation agency, private sector (consultants and contractors) and most importantly, the public. This study demonstrates a method that could be used to minimize the number of required test locations along a highway segment using common statistical techniques. It is also very timely in light of Public Private Partnerships (PPP) where friction testing at the network level will become more commonplace. This study provides much needed advice on optimizing skid testing interval requirements.