E-mobility has always been associated with hopes for quieter car traffic because electric motors do not produce any noise when starting up or setting off. An EU regulation adopted as early as 2014 has burst this illusion: according to Regulation No. 540/2014, from 1 July 2019 all newly registered hybrid electric and pure electric vehicles must be equipped with an Acoustic Vehicle Alerting System (AVAS).
‘E-mobility was of course associated with the hope that everyday life in the cities would become quieter’, confirms Siegfried Brockmann, Head of the German Insurers Accident Research (UDV). ‘But the mere assumption that an electric vehicle does not make any noise is deceptive’. He explains that from 30 kilometres per hour, the noise caused by tyres on the road due to abrasion is louder than a conventional combustion engine. The Brussels regulation has been adapted accordingly: the AVAS is permitted to switch off at speeds above 20 km/h because this ensures that the vehicle can be heard acoustically. ‘Communication is important in traffic, and experience shows that people communicate with all their senses here’.
Warning system to assist in perception
A vehicle approaching silently is a potential danger, mainly for cyclists and pedestrians but also in particular for visually impaired people. ‘It is not just associations for the blind that have long demanded such a warning system’, explains Welf Stankowitz, Head of the Vehicle Technology department at the German Road Safety Council (DVR), ‘but many other interest groups also recognise the danger’. Whether in car parks or on driveways, there are many dangerous situations in which traffic is not always visible or easy to assess. A corresponding study by the US National Highway Traffic Safety Administration (NHTSA) revealed a two-fold higher accident risk for electrically powered vehicles. There is a lack of a similar study across Europe because there are simply too few electric cars on the roads.
According to the regulation, the AVAS for electric vehicles and hybrids must be based on the noise of another vehicle. ‘Go away, I’m a Porsche’ is not permitted in just the same way as barking dogs is not permitted’, Stankowitz affirms. The sound must consist of at least two third octave bands, one of which must be below 1600 Hertz for elderly people with impaired hearing. The volume must be at least 56 decibels, but must not exceed 75dB. It is also important that the frequency increases during acceleration and decreases during deceleration.
Time gap selection restricted
‘Pedestrians orient themselves using their perception of speed’, states Brockmann. ‘We talk of a “time gap selection” that is made using the perceived speed’. The vehicle must inform the pedestrian that it is approaching faster. For Stankowitz, the new regulation does not yet go far enough. ‘There are no specifications for a starter noise, for example. You can only hear the sound when the vehicle is already moving’. Furthermore, statistically speaking, slow-moving vehicles are generally more often involved in accidents. ‘Even combustion engines have become so quiet these days that they can easily be missed’, emphasises Stankowitz However, the regulation does not apply to them, nor do older electric vehicles have to be retrofitted.
So an end to the quiet then? Not quite yet. The EU regulation stipulates that general noise pollution within the environment should be taken into account in the development of the AVAS. For the experts, this would mean a noise level that could be adapted to suit the environment. Welf Stankowitz is confident that many more optimisations will follow. ‘Once the first evaluations have been carried out, improvements can be made. Anything is better than finding out in practice that pedestrians will come to harm’.