A methodology has been developed, based on a study carried out in 1998–99, to assist in selecting optimum slope-failure preventive maintenance programmes for highways. The existing risk to road users from slope instability is first quantified, then the effectiveness of maintenance programmes in reducing the risk to road users is determined and the mitigated risks quantified. The risks are expressed in economic terms and the implementation costs associated with each programme are incorporated into the analysis.
The technique allows for the consideration of uncertainty in various input parameters (both geotechnical and economic). Monte Carlo simulation allows analysis outputs to be expressed in terms of probability distributions. The uncertainty associated with the analysis outcome may therefore be quantified, leading to better informed decision-making and prioritisation of expenditure. A Microsoft Excel 97 file has been developed to allow the technique to be applied to a range of slope stability situations.
Keywords: assessment, benefit, benefit/cost, cost optimisation, geotechnology, hazard, instability, maintenance, Monte Carlo simulation, New Zealand, probability, risk, roads, rockfall, slope