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2. Did towing vehicles occupy Lane Two excessively?

2.1 The starting point of the analysis was to see if the signs directing towing vehicles (which includes caravans) to use Lane One were effective in causing a change in lane use by towing vehicles.

2.2 From the video survey, a count was made of towing vehicles, HGVs and coaches in Lanes One and Two. Overall, in the 12-hour monitoring periods, towing vehicles, HGVs and coaches represented 5.6% of the total flow. Table 1 shows the percentage of the total flow comprising towing vehicles, HGVs and coaches for each 12-hour period of survey.

2.3 Table 2.1 shows that 'other vehicles' represented approximately 94% of all vehicles on Naish Hill during the 12-hour survey periods, most of these being cars. The proportion of coaches expressed as a percentage of the total flow was fairly consistent during the survey period at around 0.3%.

2.4 Towing vehicles represented a greater proportion of traffic volume on Saturday when compared with the Friday survey period - towing vehicles averaged between 1.7% and 2.2% of the 12-hour Friday volume midday to midnight, and between 3.5% and 5.2% on Saturdays 0600-1800hrs. The majority of towing vehicles were cars with a caravan.

2.5 Figure 2.1 shows the percentage of towing vehicles, HGVs and coaches in each lane over the eight week monitoring period. It shows that in the two weeks preceding the pilot, the proportion of towing vehicles in Lane One was between 81% and 87% of the total towing vehicle flow, with the remainder using Lane Two. The average percentage of towing vehicles in Lane One in this period was 84%. This immediately suggests that four in every five towing vehicles used the nearside lane in any case without a need for signing directing them to do so. In the following weeks (from 30 July onwards), the proportion of towing vehicles in Lane One increased to an average of 91% in a range from 88% to 94%. There was no discernible change in lane use by HGVs and coaches. Traffic congestion was still experienced in the pilot signing study period.

2.6 The fact that most towing vehicles were already using Lane One to climb Naish Hill therefore suggests that traffic congestion is not entirely due to towing vehicles using Lane Two. A similar proportion of HGVs also use Lane One, whereas the percentage of coaches in Lane Two is twice as high as that for towing vehicles and HGVs, but the total number of coaches is considerably lower than that of towing vehicles and HGVs. 

2.7 The change in the proportion of towing vehicles in Lane One from 84% before the pilot to 91% during the pilot indicates that the introduction of signs did have an effect on towing vehicle lane use, but the degree of change is perhaps not significant enough to have had any impact upon the formation of traffic congestion.

2.8 The lane use of towing vehicles was then reviewed in greater detail by comparing lane use in three periods on Fridays and Saturdays, specifically the period before the signs were installed, the period when signs were on display, and the period when the signs were removed. These periods are summarised in Table 2.2 and the percentage of towing vehicles in Lanes One and Two in each period shown in Figure 2.2.

2.9 Table 2.2 shows the three time periods considered by the study. Periods 1 and 3 are outside the period when the lane use signs were displayed. These coincide with less heavily trafficked periods, representing the shoulders of the main period of congestion which logically is Period 2 and hence when the signs were displayed. Figure 2.2 shows how the use of Lanes One and Two by towing vehicles compared in each period. 

2.10 Figure 2.2 shows a degree of variation in lane use by towing vehicles in the two weekends leading up to the pilot signing period, i.e. up to and including 24 July 2004. In the period from 30 July when the signs were displayed in Period 2, lane use is less variable and generally more towing vehicles are using Lane One even when the advisory signs are not displayed. This may be a result of the widespread publicity gained by the scheme in local and national media. In most cases more towing vehicles used Lane One in Period 2 (when the signs were displayed) compared to the preceding Period 1. For the weekend of 3/4 September 2004, the signs were not displayed, but the pattern of lane use is more similar to that from 30 July to 28 August than from 16 to 24 July 2004.

2.11 Overall, it is clear that the signing pilot did encourage more towing vehicles to use Lane One when compared to the preceding periods.