Citation

Dijkstra A. Proc. Road Saf. Four Continents Conf. 2005; 13: 9p.

Copyright

(Copyright © 2005, Conference Sponsor)

DOI

unavailable

PMID

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Abstract

The traffic flow along the motorways in the Netherlands is gradually getting less because of an increasing use and an almost constant capacity. The accessibility of the economic centers is thus coming under heavy pressure. In late 2000, TNO INRO presented a solution that, in the meantime, is known as ''Bypasses for accessibility". The main feature of this concept is the introduction of an additional system of "underlying" main roads that can handle a large part of regional traffic thus relieving the existing motorway network. According to TNO INRO, their application results in a considerable improvement to traffic flow and it also contributes to a reduction in the number of traffic casualties. However, SWOV proposes that the road network introduced by TNO INRO should meet the requirements of a Sustainably-Safe Road Traffic. In a first elaboration, TNO INRO distinguished two alternatives:1) a motorway network with extra capacity through more lanes and 2) an underlying main road network with greater capacity through more lanes and sometimes split level intersections. A comparison between both TNO INRO alternatives and the SWOV option (in which the underlying road network is designed as being sustainably-safe) shows that the safety optimization is encountered in the SWOV option, but that there is only a relatively slight resulting improvement in accessibility. Although the SWOV option has safe, split level intersections, it only has a limited capacity on road sections (one lane per direction). The opposite is true of the TNO INRO alternatives; they have a greater amount of accessibility but have a lower safety level. This is mainly because of the combination of larger capacity (two lanes per direction) and (less safe) intersections at grade. An accessibility concept, as developed by TNO INRO, deserves attention and further elaboration. For the further elaboration, seen in the Sustainably-Safe perspective, more attention is necessary for the requirements concerning: a) the mesh of the various road categories (size of residential areas, distances traveled on distributor roads compared with other categories); b) the cross section of distributor roads and regional through-roads (number of lanes per direction, lane width, with or without emergency lane); c) intersection spacing; and d) the nature of the intersections (split level or at grade, with or without roundabouts) on distributor roads and regional through-roads. The author's recommend working out a combined accessibility and safety concept that is, simultaneously, cost-effective. In this, the starting points and main principles of Sustainably-Safe must come out better than in TNO INRO's current accessibility concept.