SIGNING AND DESIGN FOR LOWER SPEEDS
Speed choice is affected by the look and feel of the road environment. Road signs play an important part in ‘explaining’ aspects of the road environment to drivers, especially maximum safe speeds. Two contrasting approaches are illustrated in this section. The first (as shown in Dorrington and Craven Arms, and in West Lothian) adapts traditional traffic calming measures by using visually striking signs and road markings. The second approach (Norfolk County Council, Starston and Poundbury) has been developed where landscape values are high and clutter or intrusion unwanted.
Where clutter is unwanted, signing can be designed so that it causes minimal intrusion and degrading of the environment. Visual design criteria are fundamental to the basic nature of speed management schemes and should be considered from the earliest stages. According to Derbyshire County Council (Derbyshire County Council, 2000), the most important consideration when positioning a sign is to set it against a backdrop so that it:
At Dorrington and Craven Arms, both straddling the A49 in Shropshire, ‘countdown’ signs specially authorised by DETR have been installed in advance of 30mph speed limits at both ends of the villages. In addition, there are ‘dragon’s teeth’ markings on the approaches to the 30mph limit signs (17 pairs in Dorrington, nine in Craven Arms), plus red patches with 30mph repeater roundels or signs at intervals through the villages (five in Dorrington, six in Craven Arms).
Although speed cushions had not previously been used on a trunk road, they were used in Craven Arms because they seemed appropriate to control speeds in the centre of the village. Four mini-roundabouts were installed as a speed reducing measure in order to comply with the Highways (Road Humps) Regulations 1990 in force at that time (subsequently superseded by the 1996 Regulations). Speeds at the Dorrington and Craven Arms gateways were reduced by between 7 and 10mph (see Table 2). The use of repeater roundels in Craven Arms also reduced speeds in the centre of the village by around 4-5mph.
Table 2: Mean and 85th
percentile speeds at Dorrington and Craven Arms gateways before and one
year after scheme installation (speed limit in both villages 30mph)
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| Dorrington |
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| Craven Arms |
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A public opinion survey carried out at Craven Arms found that around 67% of people thought the countdown signs, gateway markings and repeated red patches were useful. The mini-roundabouts were, however, criticised (DETR, 1997).
Contact:
Charging and Local Transport
Division
DTLR
3/24 Great Minster House
76 Marsham Street
London SW1P 4DR
(tel: 020 7944 2954)
4.2 West Lothian Council gateway treatments and road narrowings
West Lothian Council has carried out a series of traffic calming schemes which have used gateway treatments, road markings and road narrowings on main roads. The results from the three villages of Dechmont, West Calder and Pumpherston indicate an average 4.5mph reduction in speed, with even larger reductions (averaging 6mph) at two of the three sites studied. Table 3 shows the 85th percentile speeds, the posted speed limit being 40mph.
Table 3: West Lothian
85th percentile speeds before and after scheme installation (speed limit
at all locations 40mph)
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| Dechmont (shop) |
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| Dechmont (east gateway) |
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| A71 West Calder (Burngrange) |
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| A71 West Calder (cemetery) |
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| Pumpherston (south village) |
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| Pumpherston (primary school) |
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The Council notes that:
David Jarman
Head of Strategic Planning
and Transportation
West Lothian Council
County Buildings
Linlithgow EH49 7EZ
(tel: 01506 775 269)
4.3 Norfolk County Council interactive speed limit signs
Since 1992 Norfolk County Council has trialled the use of interactive fibre optic speed limit signs in a number of villages. The County Council has pioneered techniques of signing to elicit desired responses from motorists while conserving the rural environment. These techniques include the development of interactive speed limit signs, redesigning the road environment to make drivers think more and designating a network of ‘Quiet Lanes’ which are signed in such a way as to discourage use by motorists.
The first trial of interactive fibre optic signs, in the village of Scole, was to reinforce the existing 30mph speed limit, and was assessed through observation of speeds before and after installation. A year after installation the mean vehicle speed had been reduced by nearly 6mph, and the 85th percentile speed had been reduced by 8mph. Interactive speed limit signs have since been trialled in other locations in Norfolk (Traffic Engineering and Control, 2000).
The sign legend is a 30/40mph roundel consisting of a pictogram formed by an illuminated red-coloured circle and white numbers on a black background, matched in size as nearly as possible to a 300mm roundel. The device is activated by any vehicle that exceeds a pre-set speed threshold, detected by a radar speed discrimination detector which is mounted on top of a pole carrying the sign. This threshold is set at 35mph for the sites with a 30mph limit and 45mph for the sites with a 40mph limit. When activated, the fibre optic roundels light up from within and two pairs of amber lights are illuminated alternately above and below the sign legend.
The mean inbound speeds at all signs fell below the speed limit in all villages. There was some evidence of speed reductions in the 40mph speed limited village centres, but little evidence of any significant effect of the sign in the centres of the 30mph speed limited villages (although speeds here remained below the limit). The results from trials in six villages are illustrated in Table 4.
Table 4: Norfolk villages: mean speeds before and after interactive sign installation
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| Acle |
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| Horstead |
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| Wells |
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| Wroxham |
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| Carbrooke |
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| Swaffham |
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The percentage of inbound vehicles exceeding the respective trigger speeds of 35mph and 45mph at the signs decreased considerably. The largest change was at Acle, from 55% before installation of the sign to 7% one year after. For the 30mph sites, the overall percentage of inbound vehicles exceeding the trigger speed at the signs changed from 36% to 7% one year after. (The latter figure compares very favourably with the national average of 36% of vehicles exceeding 35mph in 30mph restricted areas.)
The corresponding results for the two 40mph sites were that an average of 20% of vehicles exceeded the trigger speed before, whereas only 6% did so one year later. (In comparison, the national average for vehicles exceeding 45mph in a 40mph area is 12%.)
Similar results from further trials have led Norfolk County Council to conclude that interactive fibre optic signs are most effective for inbound vehicles in the vicinity of the sign. A year after the installation of the ‘six village’ trial signs, statistically significant average reductions in the mean speed (-4.3mph) and 85th percentile speed (-5.9mph) of inbound vehicles were achieved, and there was a statistically significant reduction in the level of non-compliance with the speed limit. It appears that most drivers are embarrassed to trigger the sign (Farmer et al, 1998).
The effectiveness of these vehicle-activated signs is acknowledged in the government’s Review of Speed Policy. Costing £6,000 each, they are also in high demand. So far Norfolk County Council has installed 80 of them.
Contact:
Norfolk County Council
Planning and Transportation
County Hall
Norwich NR1 2SG
(tel: 01603 222 143)
4.4 STARSTON, NORFOLK: SPEED REDUCTION THROUGH DESIGN
English Heritage urges local authorities to consider the extent to which different kinds of traffic calming measures require signs. It suggests that signs should be kept to the absolute minimum required in size and number to ensure safety and comply with legal requirements, and be integrated carefully with the surrounding environment. A sign audit carried out by Devon County Council in Dartmoor National Park after the introduction of a speed management strategy and a 40mph speed limit resulted in the removal of 121 signs.
Starston is a village in Norfolk which had identified speed management as part of an overall scheme to improve non-car access to the nearby town, particularly for journeys to school. Residents were therefore campaigning for a 30mph speed limit through the village.
However, the Council considered the road through the village was too short to get the desired response: "The road environment wasn’t going to convey the right messages for that ‘urban’ speed limit." The introduction of a 30mph limit would have required 26 signs, leading to clutter.
Instead, a scheme was devised to achieve speed reduction without a new speed limit. Natural traffic calming features, such as a right-angled bend approaching a bridge, were augmented. Signing and markings were reduced: 11 warning signs were removed, including one motorway standard chevron (another chevron was kept). The centre white line was removed, except at the bend. The road surface was dressed in an attractive brown stone chosen by local people, who also commissioned a village gateway sign from a local artist. The measures achieved the desired results, as speeds through the village were indeed reduced to around 30mph.
Contact:
Norfolk County Council
Planning and Transportation
County Hall
Norwich NR1 2SG
(tel: 01603 222 143)
4.5 Poundbury, Dorset : designing new urban spaces with a human scale
Many new towns have been designed around the car, and many existing communities have been overwhelmed by the car. In recent housing schemes, roads have taken their form from the requirements to achieve movement of motor traffic. Buildings have been arranged around the car, which has inevitably led to an unnatural and inhuman environment.
At Poundbury, a new-build development which is part of the Duchy of Cornwall, a different approach has been taken. To begin with, designers have focused on creating pleasing urban spaces. Buildings have then been placed around the spaces so as to produce an overall design with a human scale.
Pavements and roads have then been fitted informally into the urban spaces so that movement of vehicles and pedestrians is safe and easy. In some places roads have greater width, providing on-street car parking. Pavement widths also vary and are particularly generous at road junctions, in order to maximise visibility for drivers.
The layout provides effective speed control without the need for additional constraints. Junctions generally reduce vehicle speeds considerably. More frequent junctions mean slower movement throughout Poundbury. Vehicle speeds are also contained by changes of surface at the entrance to squares where pedestrians have priority. Vehicles have full access, but priority is given to the creation of coherent, attractive neighbourhoods. The network of spaces at Poundbury gives a clear identity to each part of the development.
Section 17 of the Crime and Disorder Act 1998 imposes a duty on local planning authorities to exercise their function with due regard to preventing crime and disorder. There is considerable scope to meet the road safety elements of this requirement at no extra cost by designing low speeds into new-build developments from the earliest design stage, exactly as has been achieved at Poundbury.
Contact:
Ian Madgwick
Environmental Services Department
Dorset County Council
Dorchester
Dorset DT1 1XJ
(tel: 01305 224 265)
Department of Transport (1997) Traffic Advisory Leaflet 2/97: Traffic Calming on Major Roads – A49, Craven Arms, Shropshire, London: DoT
Derbyshire County Council (2000) Highway signs: Environmental code of Practice, Matlock: DCC
Department of the Environment/Department of Transport (1992) Design Bulletin 32, Residential roads and footpaths – Layout considerations (2nd edition), London: Stationery Office
DETR (1998) Places, Streets and Movement: A Companion Guide to Design Bulletin 32 (Residential Roads and Footpaths), London: DETR
DETR (2000) Traffic Advisory Leaflet 1/00: Traffic Calming on Major Roads, London: DETR
English Heritage (2000) Streets for All: A guide to the management of London’s streets, London: English Heritage
Farmer, S, Barker, J and Mayhew, N (1998) ‘A trial in Norfolk of interactive speed limit signs’, Traffic Engineering and Control, May, pp287-292
Traffic Engineering and Control (2000) ‘Fibre optic signs show excellent driver response’, pp81-82
West Lothian Council (1998) Strategic Services Committee, 17 November 1998, Traffic Calming Measures