Speed on upgrades and downgrades (ASTRA2009/010)
Overview
Background & policy context:
The speed on roads describes the driving behaviour and therefore is a fundamental value of design standards. On the one hand the speed models of the existing standards (VSS) are based on physical calculations and on the other hand on speed measurements. Latter stated values are used to compare with the models. The driving speed was mainly affected by the geometry of the roads as well as of the speed limits. Furthermore the speed of heavy vehicles affects the overtaking behaviour essentially. This manifests mainly at upgrades and downgrades, where the speed of heavy vehicles is much lower than the speed of the passenger cars. This is why the real driving behaviour of vehicles on upgrades and downgrades is repeatedly measured in the past. After the year 2005 the allocation of heavy vehicles with weights above 28t are no longer applicable. So it must be assumed that the percentage share of drives with commercial vehicles increased essentially since the year 2002. Accordingly the question at which standard the speed of heavy vehicles in upgrades and downgrades has levelled off must be stated.
Objectives:
The aim of this research project is to review respectively update the speed on upgrades and downgrades, which were surveyed in the year 2002. Therefore the surveys of traffic flow on motorways and rural roads were analysed for heavy vehicles with gross vehicle weight above 28t after the repeal of allocation, so that the results of this investigation can be compared to previous results. The priority is the crawl speed of slow and heavy loaded vehicles which travels without hindrance at the end of a sufficient long upgrade stretches at different gradients. To verify the effects at drives of heavy vehicles for the no longer existing allocation of weights above 28t, corresponding weight in motion (WIM) measurements were analysed. The WIM should be executed primary for the transalpine north-south-traffic.
Methodology:
In the study, the following steps are provided:
Step 1: Speed measurement location providing
Step 2: Evaluations
In this step, the velocity profiles along the slope distances are determined and examined the relationship between duration and size of the pitch speeds. Is also included the evaluation of weight measurements at the decisive WIM measuring points of ASTRA
Step 3: Comparison with readings 2002
The aim of the study is the comparison of any possible rate changes between the states in 2002 and today and the assessment of the impact on traffic flow.
Step 4: Reporting
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