April/May 2007

Concerns have been raised that digital tachographs record driving time in a slightly different way from analogue tachographs, and that in some cases this might work to the disadvantage of drivers using them.

The issue hinges on the fact that digital tachographs record driving time in units of one minute (a 'calendar minute', according to the legislation), and assume that any driving done in any such minute counts as a whole minute. Analogue tachographs, by contrast, can theoretically record any driving period, however short.

Among critics of this phenomenon is Gordon Humphreys, long-time tachograph analysis specialist who is now with telematics specialist RTL. 'Until the matter is tested in court, or manufacturers change technology,' he says, 'those using digital tachographs are at a disadvantage compared with those using analogue tachs.'

He says that in a stop-start operation in which a vehicle is driven frequently but for a very short time on each occasion, the discrepancy in relation to an analogue tachograph could easily mount up to around half an hour in the course of a day.

Tachograph manufacturers however point out that their instruments merely conform to legislation. Council Regulation EEC 3821/85 explicitly spells out the requirement, stating for instance: 'Given a calendar minute, if any driving activity has occurred within the minute, the whole minute shall be regarded as driving.'

Changes to this effect were assimilated into UK law in subsequent legislation.

In any case, the changes do not all work against drivers. Derek Beevor, head of software house and tachograph specialist Road Tech Computer Systems, points out that in the past, time spent by drivers standing still in a traffic jam would all count as driving time, whereas digital tachographs record any stationary period beyond two minutes as 'other work'. He argues: 'It's really a case of swings and roundabouts.'

He also points out that not all analysis of analogue tachographs is accurate down to the second. 'Some analysers use a visual rule which has the thickness of a whole minute,' he maintains, 'and in the past a lot was down to the judgement of the person doing the analysing.' He insists, however, that his firm's recently-launched Tachomaster service can offer accuracy down to 15 seconds on digital charts.

He also says the law on digital tachs helps reduce the amount of data that needs to be held. 'Recording driving time down to the second would vastly increase the data storage requirement.'

However, Gordon Humphreys warns operators of the need to beware of the situation - which, he argues, 'goes against one purpose of the legislation - to harmonise conditions of competition.' He says diligent training and watchfulness are required to ensure operators and drivers stay on the right side of the law.