Barrack Street, Perth

A9 Safety Group

Tuesday12th November 2013 at 10:30

Barrack Street, Perth

Attendees:

Notes of Meeting

Stewart Leggett welcomed and thanked everybody for attending the meeting at short notice and also thanked Police Scotland for providing meeting facilities following whichintroductions were made around the table.

Stewart Leggett advised that there is still the next full meeting of the Safety Group on the 26th of November; howevercolleagues in AECOM and TRL have been doing a lot of work on updating the traffic model and understanding the results from it. Given the level of interest and demanding programme for implementation of the average speed cameras it was felt worthwhile to have an early meeting to hear the results and have a discussion around them would be helpful before the next meeting as there is still a lot to discuss on the communications side.

It is known that the average speed cameras will bring considerable safety benefits to the route and there has been a lot of discussions on the pro’s and cons of retaining 40mph for HGV’s or increasing it to 50mph which today’s presentation will help form the debate / discussion.

Phil Flanders asked if data will be available to take away. Stewart Leggett responded that report was still in draft, will not get it today but it will hopefully be issued by the next meeting.

Stuart Wilson outlined the format of the modelling presentation and introduced the team from AECOM (Neil Halkett / Simon Hardie) and TRL (Brian Walton) involved in preparing the (evidence based) model

Alison Irvine provided a summary of the data collection procedureexplaining that over the last twelve months Transport Scotland have developed a new paramics model of the A9 primarily for the A9 Dualling programme. It is the best available model – using the most appropriate software and up to date information gathered.

Information was gathered using ANPR (12hr survey), Bluetooth (10 day period covering 70 sites on the network including the A96), overtaking and passing manoeuvres (3 locations – Crubenmore Dual Carriageway, Ralia straights and 2+1 and Inshes 2 +1).

Alison Irvine finished by saying that the model can predict impacts but not behaviour of traffic and that this is the first commercial use of the software to test Average Speed Cameras.

Neil Halkett said that AECOM were brought in to model the impact of average speed cameras on the A9.

A number of scenarios / methods were tested – using evidence based data from the A77 Average Speed Cameras and also data collected from the various surveys on the A9 as highlighted by Alison Irvine.

Amongst the outputs looked at were Overtaking and Passing, Platooning, Journey times, Speed distributions/Speed differential.

BrianLawton (TRL)presented data on the accident analysis- covering various model scenarios (covering a weekday 7am to 7pm). Speed is a critical factor as part of accident analysis and the analysisundertaken in this case was based on change in average speeds only. The safety effects of changes to speed differentials and overtaking could not be quantified.

The safety analysis undertaken by TRL, based on the forecast change in average speeds, indicated that accident savings are forecastthrough the installation of average speed cameras, whether existing speed limits are retained or the speed limit for HGVs>7.5T is increased to 50mph. However based on this analysis of change in speed, the greatest accident savings are forecast through the delivery of average speed cameras alongside retention of the existing speed limits.

No reliable evidence from the accident study that there is a correlation between a reduction of overtaking manoeuvres and accidents therefore from a scientific point of view a pilot could be worthwhile.

A Question and answer session followed with members of the group after which Stewart Leggett thanked AECOM and TRL who then left the meeting.

Stewart Leggett said there was a lot of information which to take in. The following points were noted from an operational and safety perspective:-

• The horizontal and vertical geometry of the A9 single carriageway sections between Perth and Inverness are to a consistently higher standard than other single carriageway trunk roads. As such it provides the safest infrastructure with which to conduct a trial.

• The micro simulation modelling already conducted on the A9 shows clear operational benefits for the A9 from an HGV speed limit increase, primarily around journey times.

• The A9 Dualling Programme and the Average Speed Camera preparatory work have given rise to a huge wealth of research studies and an exceptionally expansive system of speed and traffic monitoring equipment. This provides a remarkably good framework with which to evaluate the impacts of a pilot.

• The introduction of a 50mph speed limit for HGV’s when supported by Average Speed Cameras will improve safety over the current situation.

• Due to the functionality of the model software, a number of parameters affecting driver’s behaviour have been adjusted to match expected behaviour with the two scenarios in place. As such, a number of the elements which influence driver behaviour have been prescribed rather than revealed. This was necessary to emulate the impact on speeds we have seen on the A77, but has the potential to impact other model outputs.

• There has been significant concerns raised by road users, the haulage industry and elected members at the potential consequences of effective enforcement of HGV’s at 40mph. They feel strongly that it will increase frustration, lead to more overtaking and ultimately a higher number of serious injuries.

• The modelling has tried to consider likely change in overtaking behaviour but the outcomes are largely user defined. If driver ‘aggression’ remains at current levels, after the introduction of the average speed cameras and enforcement of HGV’s at 40mph, the modelling shows the number of vehicles overtaking will be marginally higher than it is at present.

• The traffic model has limitations and does not fully consider what influence a change in overtaking behaviour will have on the road safety performance of the A9.

• A reduced speed differential could have a positive road safety benefit. Variations around the average speed of travel, above or below, are associated with an increase in the rate of accidents. This is linked to an increased interaction amongst vehicles and the behaviour of those with a desire to overtake.

• The posted speed limit difference (below the average speed) would reduce to just 10 mph by the introduction of a HGV 50mph pilot. The modelled safety benefits do not take into account what influence the speed difference has on the road safety performance.

• The speed cameras eliminate the highest risk excessive speeders yet the safety impact only considers a change in the average speed

• The Scottish Government has committed to installing Average Speed Cameras on the A9 and this will provide a controlled and safer environment in which to conduct the trial.

A further discussion took place over pro’s and cons of the information presented.

Stewart Leggett asked for the Group member’sviewsbased on the data presented and bearing in mind that group members had not yet had the opportunity to review the emerging modelling report : ‘Following the additional modelling work, do you support a pilot for an increase in the speed limit of HGV’s over 7.5 tonnes to 50mph for the A9 between Perth and Inverness within the extents of the Average Speed Cameras’

1Discount implementation of 50mph HGV pilot

2Enforcethe existing 40mph HGV limitfor a period from commissioning the Average Speed Cameras before implementing a 50mph HGV pilot.

3Implement a 50mph HGV pilot from commissioning the Average Speed Cameras

Some members of the A9 Safety Group saw merit in a pilot 50mph if the Average Speed Cameras operated at the existing speed limits for a period first (Option 2) It was suggested that observations of the operation at existing speed limits first to see if driver behaviour problems persisted before confirming a move to trial the 50mph may offer the best approach.

Other members indicated that their preference would be to retain the HGV 40mph limit (Option 1), given that their only consideration was that of safety, and that the evidence available suggested that retaining the 40 mph speed limit under the operation of average speed cameras would return the greatest accident savings.

A number of points were raised, including comments that higher speed required more time to complete overtaking manoeuvres and increased the approach speed of vehicles. Also, it was noted that there is little published evidence on the relationship between speed differentials and overtaking and the consequential impacts on safety.

Stewart Leggett thanked everybody for their attendance and for their consideration of the traffic modelling work. He reminded everyone the next meeting of the group is on the 26th November and that he looked forward to continuing discussions.

Page 1 of 4