Comparison of In-Vehicle Technologies with Traditional Safety Measures to Prevent Crashes along Curves and Shoulders

Abstract

Five hundred and ten people were killed in the state of Minnesota in 2007. Using MN/Dot values for crashes this costs the state more than $3.5 billions. Forty percent of these fatal crashes are road departure crashes and they mainly occur on rural roads. To prevent these road departure crashes and reduce the financial losses occurring due to them, safety systems have to be implemented. There are two types of systems which could be implemented: · Traditional civil engineering solutions such as adding rumble strips, curve flattening, shoulder paving etc. · Emerging technology-based solutions. The technology-based safety systems consist of both infrastructure-based and in-vehicle systems. The technology-based infrastructure solutions involve radar based advanced curve warnings where the speed of the vehicle is calculated and if necessary the driver is warned. In-vehicle technologies include both vision-based and DGPS-based lane departure warning systems. Owing to the limited budget and necessity in curtailing the number of fatal crashes, these safety systems have been compared and studied to suggest an optimal solution which would be cost-effective and also effective in reducing traffic fatalities due to lane departures. Presented herein is a follow up on a research initiated by CH2MHill [1.]. A sample set of 204 curves and 137 tangential sections was studied by them. Their research mainly consisted of two parts: iv · A cross-sectional study to evaluate the effect of road geometry such as curve radius, width of shoulders, etc. on road departure crashes. · A before:after analysis which studies the effect of certain civil engineering treatments in form of crash rate on the road section before and after implementing the treatment. Based on the cross-sectional and the before:after analysis, the traditional safety treatments identified on road sections were evaluated against new technology-based safety systems through the following approach: · Effectiveness – Effectiveness of any system is the extent to which it meets the purpose, in this case, the extent to which it reduces crashes. The effectiveness was quantified for each safety system using either the before:after analysis, values provided by FHWA or analogies drawn on reduction in fatalities due to existing technologies such as seat belts and ABS. · Exposure – Effectiveness of any technology is always a function of its exposure. This exposure is measured in terms of the number of vehicle miles the system is exposed to, public acceptability and market penetration. · Cost-effectiveness –It is necessary to implement safety systems which are cost-effective for the government as well as the public to ensure effective use of the financial resources. Any change on the roads is cost-effective for the state if the money spent on implementing the change is compensated for by the reduction in losses occurred to the state due to crashes and fatalities. Benefit:cost ratios have been calculated to evaluate this cost-effectiveness. · Contribution to TZD – The state expends a fixed amount of safety budget every year. Thus, given a fixed amount of money, the treatment giving the most reduced number of fatalities was evaluated. This was defined as the deployment factor. The treatment having the highest deployment factor was the optimal solution which would help to move towards Mn/DOT’s goal of Towards Zero Deaths (TZD). Result In this study, new emerging technologies were studied against traditional infrastructure based safety systems. These studies were evaluated based on their effectiveness in reducing crashes, market penetration, legal implications, cost effectiveness and their contribution to TZD and an optimum solution has been provided. For curves, curve flattening produced highest effectiveness of 66%. However, curve flattening is among the most expensive safety treatment. Using effectiveness numbers from the FHWA, static curve warning systems would appear to provide the highest benefit:cost ratio. However, it is important to note that as a result of the cross-sectional and before:after analyses, approximately 80% of the curves studied were already equipped with static curve warning signs, and these intersections still had high crash and fatality rates. Hence the deployment factor was calculated for all the remaining safety systems maintaining the static signs as the baseline. For a given fixed safety budget, vi adding rumble strips gives the highest reduced number of fatalities or the highest deployment factor. Similarly, for tangential sections, enhancing them gave the highest deployment factor. Also, evaluation of the in-vehicle technologies showed that the vision-based lane departure warning systems have deployment factors comparable to that of enhancing the road sections. These results were obtained based on the data set that has been the background for our research. The above approach however should not be limited to one particular data set and can be used by engineers as a generic tool and approach to evaluate different safety systems for their cost-effectiveness and contribution to reduction in fatalities.