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
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
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:
· 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
· 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
· 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
· 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).
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,
adding rumble strips gives the highest reduced number of fatalities or the highest
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
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.
University of Minnesota Master of Science thesis. December 2009. Major: Mechanical Engineering. Advisor: Craig Shankwitz. 1 computer file (PDF); xii, 131 pages.
Pitale, Jaswandi Tushar.
Comparison of In-Vehicle Technologies with Traditional Safety Measures to Prevent Crashes along Curves and Shoulders.
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