BARCLAY TRAFFIC PLANNING

RESEARCH ...page last updated 19 December 2008

Barclay Traffic Planning has an active programme of research into technical and policy issues, to complement and support its service to clients. Recent research projects include:

Rail level crossings. We have made a submission on the Manual for Traffic Control Devices Volume 9: Level Crossings draft guideline released for consultation recently by Land Transport New Zealand. The submission raises a number of concerns, especially in relation to the use of "Give Way" and "Stop" signs at rail crossings. The final version has now been published.

New Zealand Planning Institute Conference 2003 In May 2003 Bill Barclay presented a paper on transportation planning to the New Zealand Planning Institute annual conference in Hamilton. 2003 was the 50^th anniversary of the enactment of the Town and Country Planning Act 1953 which can be regarded as the foundation of modern town planning. To mark the occasion the conference adopted the theme “50/50 Vision”. Bill’s paper focussed on demographic, economic and technological changes since 1953, and their implications for transportation planning. Rapid growth in travel demand has been fuelled by changes in the work force and a major expansion in the volume of freight. In terms of energy efficiency, road transport is now competitive with rail for both freight and passenger transport. The paper proposes a hierarchy of transport modes, in which the most economical and flexible modes such as walking, cycling and road transport are exploited first, before resorting to more expensive modes such as rail.

A graph in the Planning Institute paper compared trends in petrol prices and energy use over a period of 30 years. At the time of the conference in 2003 petrol prices in real terms were very low, in fact at about the same level as in 1971 prior to the first oil crisis in 1973. Since 2003 there have been sharp increases in fuel prices, and an updated version of the graph below shows the trends to 2008. The graph does not show reductions in price during the last months of 2008.

There has been a sharp increase in fuel prices but real cost is still well below the peaks of the mid-1980s. There are signs of some moderation in the growth of energy use, but higher prices have not prevented a continued upward trend.

Simulation models Since 1989 we have been developing traffic simulation models, for analysis of gap acceptance behaviour (SIMGAP), and movement of vehicles through a network (SYMPATHY). These programs differ from many commercial packages in that they are event-scanning models rather than time-scanning. (The simulation moves from decision-point to decision-point with time increments of variable length.) This method offers advantages in both power and accuracy.

SIMGAP models traffic gap acceptance behaviour, which is the key to understanding much traffic interaction. It represents gap acceptances of non-priority vehicles in a priority stream directly, and can be configured with multiple lanes and headway distributions that can be random, uniform or platooned.

A feature of SYMPATHY is the use of acceleration functions based rigorously on Newton’s Second Law. This makes it well suited for route comparison calculations of time and distance.

Information on these research topics is available on request.