Local highway authorities could save £35M a year by dimming streetlights when roads are lightly-trafficked, while still maintaining road safety and pedestrian security, according to the County Surveyors’ Society.
Research carried out by TRL for the CSS and partners suggests that installing systems to control the lighting levels of lamps from afar is now becoming cost-effective, due to the reliability of the latest electronic control gear and communication systems.
Varying lighting levels according to traffic flows could save £1,556 per km per year, and installation costs on a typical 2km route would pay for themselves in less than five years, TRL suggests.
However, fewer than half of councils (47%) are considering introducing central control and management systems, with authorities believing that the technology remains costly, is not yet reliable, and would be unsuitable in dispersed, rural counties.
Dana Skelley, chair of the society’s streetlighting working group, said: ‘The chance to gain major savings from tax spend, carbon dioxide and light pollution, while still offering effective streetlighting, is a fantastic step.’
Dimming on residential streets, by contrast, would only save around £492 per km, but TRL highlights that this would be nearly as much as the £740 per km saved by switching lights off in the early hours of the morning – and more politically acceptable.
Switching lights off between midnight and 5am is not recommended on traffic routes by TRL, because ‘when traffic flow is at its lowest, vehicle speeds will be at their highest, so the accidents will be more severe’. The advice – which was also commissioned by Highways Agency and Scotland’s roads authorities – says if part-night lighting is considered, this should be based on ‘a full evaluation of the accident statistics’. The HA has announced a trial on a section of the M4 near Bristol and on part of the M5 near Exeter.
TRL’s survey found that 67% of highway authorities are considering replacing old, inefficient luminaires, and 73% the old electromagnetic ballasts which control when lights come on and off.
The studies were ordered following industry concern over councils turning or decommissioning lights. Torfaen County Borough, for example, is consulting on plans to switch off up to 50% of lights, including on A and B roads. But Cardiff City Council will not proceed with an early-hour switch-off, after there was a fatal accident during a trial on a traffic route.
Gloucestershire County Council, meanwhile, is to dim 10,000 lamps, and switch a further 7,000 to part-night operation.
The TRL reports, including Guidance on financial returns from spend to save initiatives, are available here.
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