Daytime Running Lights (DRL)
Dedicated, low energy front lights that switch on automatically
Early systems
The Volvo 240 was the first car in Britain which ran with lights on all the time that the engine was running. Although they looked like sidelights these were in fact separate 21 watt bulbs fitted alongside the standard 5 watt sidelight bulb within each front sidelight unit. The brighter bulb was lit all the time unless the driver manually switched on the sidelights.
In the mid-1980s UK plans to introduce 'dim-dip' lighting, not for daytime use but for use in urban areas at night, were scuppered by a failure to agree common standards across Europe. 'Dim-dip' switched on the headlights at a reduced brightness when the ignition and side lights were switched on. At this time Volvo and others adopted dim-dip in place of the 21 watt side lights for daytime running.
Daytime use of headlights
There followed much discussion over whether cars across Europe should have their headlights on all the time the engine was running – many countries introduced local rules while the European commission considered possible pan-European rules and compulsory technical standards for new cars.
By 2006 12 countries required drivers to drive with their headlights on all year round including Sweden since 1977, Iceland, Latvia, Macedonia and Norway since around 1980, Denmark since 1990 and Romania, Slovenia and parts of Portugal since 1998.
Four – Lithuania, Poland, Slovakia and the Czech Republic – required this in the winter only while Hungary and Italy required daytime running lights outside built up areas.
The UK never introduced a daytime running light rule.
Benefits of DRL
Those in favour of daytime running lights claimed a potentially significant reduction in road deaths and serious injuries while those against objected to the constant glare of headlights and voiced concern that motorcycle riders may become less conspicuous if everyone else's lights were on at the same time as their's. There was some concern over increased fuel costs too.
In 2006 the European Commission published the results of research into the effectiveness, costs and benefits of introducing Daytime Running Lights (DRL).
This report suggested that a substantial number of casualties could be prevented across the EU and showed a positive benefit to cost ratio when the costs of fitting lamps and the environmental cost of running them was considered.
A Department for Transport (DfT) commissioned study of the Commission's research confirmed that there would be a net reduction in accidents from compulsory fitting of DRL but cast doubt as to whether the benefits would outweigh the costs.
This UK report did however conclude that dedicated Daytime Running Lights could be designed to improve the visibility of cars in dim light without reducing the conspicuity of motorcyclists. It said that the use of dedicated, low intensity DRLs would be of benefit without having a negative effect on motorcycle visibility.
Legal Directive
In September 2008 the European Commission adopted a proposal for a Directive that will introduce dedicated daytime running light (DRL) on all new types of passenger cars and small delivery vans from February 2011 onwards. Trucks and buses will follow from August 2012 onwards.
There will be no requirement to retro-fit daytime running lights to existing cars and no Europe-wide requirement for drivers of cars without dedicated daytime running lights to drive with headlights on during the day.
Where fitted, dedicated daytime running lights will switch on automatically when the engine is started.
Effects on fuel consumption
We expect future designs of DRL to be similar to current examples such as the Audi S4 pictured above which consists of a row of Light Emitting Diodes (LED) which only consume a fraction of the electricity taken by a normal headlight.
Use of dedicated DRLs instead of driving with headlights or sidelights on will also mean that tail lights and instrument lights are not illuminated during the day.
The alternator is driven by the engine and spins all the time but it doesn't always consume the same amount of power from the engine. When the electrical load on the alternator increases more power is required to turn it and so fuel consumption is increased.
Whereas headlamps consume 110 watts of power dedicated DRL LEDs might consume only 5-10 watts so putting negligible load on the alternator.
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16 December 2008