Traffic load enforcement for bridge and highway management

A novel total highway cost modelling approach that accounts for the costs borne by highway owners and truck operators is presented. The approach can predict the load limit and enforcement level that corresponds to the optimum total cost. Methodologies for investigating the impact of load limits and enforcement levels on bridge network risk, pavement cost and vehicle operating cost are developed. A relationship between enforcement cost and violation rate, required for evaluation of total highway cost, is derived. Highway cost optimization based on bridge risk and pavement cost considerations only, neglecting vehicle operating cost, leads to the incorrect decision that enforcement effort should be maximised to minimise overall highway cost. If vehicle operating cost is considered, however, the optimum total cost corresponds to the “do nothing” option of no enforcement.; The effectiveness of posted load limits in enhancing bridge reliability is investigated. Novel analytical expressions are derived for event and annual maximum GVW distributions that account for violation of posted load restrictions. Annual reliability indices achieved at posted loads computed using typical bridge posting criteria, and accounting for violation of posted loads, are compared to a target reliability index. For the case of perfect compliance, the posted limit can significantly reduce maximum annual live load effects and so enhance the reliability. Under imperfect compliance conditions, however, the effectiveness of bridge posting in enhancing reliability is questionable.; Traffic load data from a 1995 Ghanaian survey are presented and analysed. The associated annual maximum force effects do not exceed the BS5400 loading commonly used for bridge design in Ghana. However, adverse combinations of load and volume growths of the heaviest truck configurations could cause governing BS5400 design loading to be exceeded. Annual maximum moments caused by the heaviest Ghanaian configuration type are similar to CHBDC and AASHTO bridge design moments, for 5–40m simple spans.