Hi Loes,

The original Road transport Association of Canada (RTAC) study which led to the HVTT conferences and various subsequent studies on performance-based standards including the Australian PBS system include a number of performance measure relating to the road space requirements of heavy vehicles.  The Australian PBS system currently includes the following measures:

Low speed offtracking

Front swing

Tail swing

High speed transient offtracking

Tracking ability in a straight path.

The first three of these relate to low speed turning performance.  This is primarily the width requirements at intersections and roundabout etc but they also affect the road width requirements in lower speed (less than 50km/h or so) curves.  The fourth one relates to the road width required during an evasive manoeuvre and thus is probably not directly relevant to lane width requirements.  The final measure relates to the road width requirements at high speed on a straight road in response to road unevenness and cross-slope.  This measure is quite correlated to high speed steady offtracking which is the road width required when traversing a high speed curve at steady speed.  In my view high speed off-tracking is a better measure than tracking ability in a straight path.

For each of these measures the Australian PBS system sets maximum allowable levels for four different categories of road.  In the research undertaken to establish the PBS system the performance of the Australian heavy fleet with respect to all the performance measures was assessed by computer simulation.  These results were used to determine the critical levels for each of the performance measures.  All of the research reports associated with the work are available on-line at the National Transport Commission web-site http://www.ntc.gov.au/DocList.aspx?SectionId=039 .  Unfortunately they are no longer catalogued separately but if you follow the link to NTC Reports, the work was done between 2000 and 2003.  Most of the relevant report are in the 2001 reports section.

In New Zealand we have also done some work looking at the road width requirements for longer vehicles.  This study was a mixture of experimental testing and computer simulation.  Experimental measurements can be done relatively easily.  We built an apparatus using a pair of garden sprayers with some relay valves and some pipe work so that we could spray thin water or paint lines on the road from the front axle and the rearmost  axle.  The offset between these lines gives the additional (over above the vehicle width) road space required by the vehicle.  We have used this apparatus for a number of vehicle tests.  It was cheap to build, is simple to fit to a vehicle and easy to use.  I have attached a report on the validation exercise comparing the computer simulations with the measurements.  There are further reports on this work if you need them. 

I think there are two issues to be addressed.  The first is how much width do the vehicles actually need and the second is then how much additional space do the drivers and other motorists need to feel comfortable and safe at the design speed for the road.  The physical requirements needed for the vehicles can be determined from the standard performance measures.  It is not too difficult to work out which are the worst case vehicles and to determine their performance characteristics by computer simulation.  It is also relatively simple to validate the simulation approach with some physical testing if this is needed.  However, the human factors side of how much additional space motorists require to feel  comfortable travelling beside a large truck at highway speeds is more complicated.  I am not aware of any work that has been done on this but there may well be some.  One option is to use a driving simulator – we have one available here but it is probably of limited use for determining how Dutch motorists will react to narrower road lanes with adjacent truck traffic.  There must be simulators available in the Netherlands.

If you need any additional information or research reports please get in touch.

Regards,

John de Pont

Director of Engineering Research

TERNZ Ltd

The Telco Building

16 Kingston St

PO Box 106573

Auckland

NEW ZEALAND

t +64 9 3370542

m +64 27 2767602

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