An Assessment of the Impact of Average Speed Cameras on Driver Behaviour on the A9(T) in Scotland

An Assessment of the Impact of Average Speed Cameras on Driver Behaviour on the A9(T) in Scotland


Cath Farrugia, AECOM, Stuart Wilson, Transport Scotland


This paper reports on Before and After surveys with drivers, plus independent monitoring data, and highlights the impact of Average Speed Cameras on driver behaviour on the A9(T)


The UK’s largest Average Speed Camera scheme was introduced along the A9(T) between Perth and Inverness in October 2014 as an interim road safety measure in advance of the dualling programme. Alongside this, the speed limit for HGVs above 7.5 tonnes was increased from 40mph to 50mph on single carriageway sections of the route. As part of the evaluation Transport Scotland were keen to understand the perceptions of A9(T) users.

Two phases of research were commissioned by Transport Scotland:

• ‘Before’ in April/May 2014 involving 296 face to face interviews with respondents who had driven on the A9(T) between Perth and Inverness within the last 24 hours, to gauge effects measures may have on drivers’ perceptions of safety and driving experience on the route; and

• ‘After’ in February 2015 which involved 302 face to face interviews in the same locations to measure changes in attitudes and behaviour of drivers on the A9(T) between Perth and Inverness.

These results have subsequently been enhanced by monitoring data from Transport Scotland to show the impact of the average speed cameras over a full 12 month period.

This research has shown positive results:

Speed Limits

• 36% of car drivers exceeded speed limit (Transport Scotland research)
• 8% of respondents did not know the correct speed limit on single carriageway sections (Phase 1)
• 31% of respondents did not know it for dual carriageway sections (Phase 1).

Propensity to speed on the A9(T)

• Respondents never exceeding the speed limit by more than 15mph increased from 43% (Phase 1) to 75% (Phase 2)
• Respondents never exceeding the speed limit by more than 10mph increased from 37% to 56%

In both phases, the majority of respondents sped because they felt it was safe to do so (94% before, 90% after).
Speeding behaviours had reduced noticeably in Phase 2:
• 83% to 47% for ‘feeling pressured by following traffic’; and
• 85% to 61% for ‘to make up for time stuck behind a slow moving vehicle’.

Own driving behaviour along the A9(T)

There was an increase in respondents in Phase 2 never ‘overtaking on dual and single carriageways’ and a decrease in respondents ‘abandoning overtaking manoeuvres’ and ‘feeling frustrated by the lack of opportunity to overtake’, suggesting the desire to overtake has reduced.

Witness of different types of risky driving behaviour

Incidents of respondents witnessing ‘risky driving behaviour’ on their last journey had decreased among respondents in Phase 2. Significantly more said they had never seen the following on their most recent journey along the A9(T):
• vehicles travelling at excessive speeds (3% saying ‘never’ before, increasing to 11% after);
• overtaking when risky (4% to 13%);
• other drivers being cut up (2% to 19%);
• a vehicle being tailgated (4% to 14%);
• road rage or aggressive behaviour (6% to 19%); and
• vehicles failing to complete an overtaking manoeuvre (4% to 14%).

Enjoyment, satisfaction and safety when travelling along the A9(T)

Phase 2 showed respondents’ enjoyment, journey time satisfaction and feelings of safety had all increased since Phase 1. On a five point scale, mean enjoyment had increased from 3.17 to 3.76, satisfaction with journey time from 3.20 to 3.75 and feelings of safety from 3.23 to 3.79.

Effect of Average Speed Cameras (ASCs) on the A9(T)

Seven out of ten respondents said ASCs on the A9(T):
• made them less likely to exceed the speed limit;
• made them feel safer than if average speed cameras were not there; and
• meant they felt less likely to be involved in an accident.

Transport Scotland’s most recent data (A9 Safety Group) (January 2016) provides strong evidence to support these survey findings.


The Overall findings suggest unsafe and undesirable driving on the A9(T) has reduced since the introduction of ASCs, including users travelling at excessive speeds of 15mph or more above the limit. Enjoyment, satisfaction and safety have also increased.

The recent A9 Safety Group data supports these survey findings that ASCs appear to have realised a positive change in driver behaviour and driver safety when travelling along the A9(T); even if it maybe difficult to ascertain exactly whether this is down to the presence of ASCs, other factors or both.

This research is of interest to policy makers and road safety practitioners.


Association for European Transport