01004452

Component

To limit the costs for the new 2nd Coentunnel, steeper grades are considered than the maximum values mentioned in the guidelines: 6% instead of 4.5%. Steeper grades reduce the length of the tunnel and its entrance road sections, and save construction costs. On the other hand, steeper grades may result in a decrease of traffic safety and traffic flow rate. This contribution focuses on determining the optimum vertical alignment in tunnels, taking into account traffic safety, traffic flow, construction costs and operation costs. The results of traffic flow and traffic safety calculations are used in a custom-developed decision support system (DSS). This system for evaluating vertical alignments, consists of three modules: a quantitative risk module, a cost-benefit module and a sensitivity module. DSS evaluations show that the number of extra accidents and casualties on the alignments with the steeper grade are limited. As a result, extra damage and accident costs are also limited. From the cost-benefit analysis, it can be concluded that extra costs for traffic accidents and congestion, because of the steeper grade, exceed the saving in construction costs by far. The sensitivity analysis shows variations of the input data have relatively little influence on this outcome. The case of the 2nd Coentunnel shows that state-of-the-art tools enable a quantitative approach to cost-sensitive design of vertical alignments.

01004374

English

18p

2005

3rd International Symposium on Highway Geometric Design

CD-ROM

Figures (6) ; References (7) ; Tables (5)

Benefit cost analysis; Cost effectiveness; Decision support systems; Highway design; Operating costs; Optimization; Risk analysis; Sensitivity analysis; Traffic flow rate; Traffic safety; Vehicular tunnels

Construction costs; Vertical alignment

Netherlands

Design; Highways; I20: Design and Planning of Transport Infrastructure

TRIS, TRB, ATRI

Sep 28 2005 11:06AM