John's cover image
John

John Gaffney

Year of Award: 2016 Award State: Victoria None > Education
None > Engineering
None > Policy
None > Science
Transport And Infrastructure > Road
To research the effects of vehicle lane changing on freeway capacity and road safety - France, Norway, Sweden, Netherlands, Belgium, Germany, Italy, Greece and Israel.
Download

Keywords: Road Safety Science, Motorways, Freeways, Traffic Theory, Behavioural Science, Attribution Theory, Crash Risk, Vehicle Design, Moose Test

 

This report presents the findings of 2016 Churchill Fellowship to study the topic of “Road Safety and Urban Motorways” which involved meetings with a wide range of road safety professionals from nine countries: France, Norway, Sweden, Netherlands, Belgium, Germany, Italy, Greece and Israel.

 

Casualty crash numbers on urban motorways in Australia are rising, growing by up to 40% in the past decade. The findings of this report suggest crashes will continue to rise without a response that effectively manages the underlying cause for where and when crashes occur. Urban motorways are the “heavy lifters” of road transport as they typically comprise about 7% of the lane kilometres,yet carry up to 40% of the travel in urban areas. Urban motorway crashes comprise around 15% of urban Fatal and Serious Injury (FSI) crashes. Hence this is a significant problem to investigate and findings suggest there are learnings applicable to crashes on the broader road network.

 

The conditions that lead to most casualty crashes primarily arise from increasing traffic demand which activates certain “Events of Exposure". These events significantly increase crash risk and, at a faster rate than growth in Annual Average Daily Traffic (AADT), and arise rapidly when motorways carry more than 90,000 vehicles each day or when traffic volumes reach 60-70% of the maximum capacity flow and when average speeds are above 70km/h and well below the speed limit. Importantly the learnings from this study have wider application: wherever these traffic conditions occur for at least some part of the day on rural freeways or divided highways, the crash risk will rise. Events of Exposure often happen within fractions of seconds, and are measurable providing researchers with a proper definition of relationships between exposure and risk. This re- establishes the connection between the basic concepts of accident research and probability theory.

 

For many years road safety programs have primarily focused efforts and resources on treating the more serious crashes only, by reducing their impacts. It has become clear in the course of this study that all motorway crashes are potentially dangerous, thus the potential for all crashes must be managed. Most urban motorway crashes (i.e. >75%) are between two or more vehicles and triggered by similar circumstances. Across the distribution of all crashes we cannot reliably predict the outcome of one crash resulting in a fatality and the next resulting in vehicle damage only. These crashes continue to occur despite improvements in infrastructure solutions, vehicle technologies and driver training.

 

The potential for all crashes needs to be managed because the mechanisms involved in crash causation come without warning often giving drivers little or no reaction time. Most motorway crashes occur under a complex regime, comprising similar conditions (i.e. moderate speeds, moderate traffic volumes, high levels of necessary lane changing required to fill up the motorways to capacity), combined with drivers’ regulating their individual speeds by minor braking and acceleration movements, numerous blind spots as vehicles travel closely together reducing the amount of empty road space. This is compounded by unpredictable and dangerous “Nucleation Events” and separate and independent “Shockwave Events” which usually come by surprise and without warning. Most of these crashes do not involve impacts with traditional road safety infrastructure (i.e. safety barriers.)

 

When crashes occur, differences in outcomes often relate to: the chance availability of a few extra square metres of empty carriageway space, (i.e. stopping or crash avoidance space); the individual driver alertness and driving capability; and the vehicle’s unique braking and handling performance in the moments before the collision. Sometimes these events combine favourably, enabling the driver to reduce the contact area between vehicles to be just a few centimetres resulting in “property damage only” crash. However if the contact area is greater than say 20-30 centimetres  these crashes may cause major vehicle structural damage transferring forces to the vehicle occupants resulting in serious injuries. Therefore all motorway crashes are potentially dangerous and efforts must focus on reducing their numbers. Even a minor crash on an urban motorway has the potential to cause widespread congestion and economic loss, often shutting down major parts of a capital city. During these events, traffic is often diverted onto secondary roads that are statistically four to five times more dangerous for fatality crashes per kilometre travelled, and thus avoiding all motorway crashes by managing their potential should be seen as important as managing traffic on the road network.

 

Many important pieces of the puzzle were identified throughout the Churchill Fellowship and are contained in the full report. When time was taken out to reflect on what were the most crucial issues it was possible to see that, whilst most of the issues apply directly to road safety on urban motorways, a number of important issues also have relevance to the wider field of road safety in Australia.

 

[See full report for footnotes for above]

Related fellows
Benjamin Newsome, Benjamin
None > Education
None > Science
2013
Catherine Doherty, Catherine
None > Education
2016
Rod Hannifey, Rod
Transport And Infrastructure > Road
2016
Melissa Latter, Melissa
None > Science
2016
Gina Dal Santo, Gina
None > Education
2015
Donna Mayhew, Donna
None > Policy
2015
Corrine McMillan, Corrine
None > Education
2015
Trevor Rapson, Trevor
None > Science
2015
Robert Lawson, Robert
None > Education
2017
Reece Hinchcliff, Reece
Transport And Infrastructure > Road
2014