Dozens of people are killed each year and about three hundred injured by the use of mobile phones in traffic. Especially because a driver was distracted while carrying on a telephone conversation.
There is a lot of case law concerning employers’ liability for injuries an employee sustains through a work accident. The liability can be very extensive. It is therefore possible that an employer can be liable (under some circumstances) for the injuries an employee sustains when they cause an accident while making a telephone call in the car in the performance of their duties. Therefore, employers would be well advised to give employees clear instructions for the use of mobile telephones in the performance of their duties.
There are already some large employers (Shell and BP) who even prohibit their staff from making telephone calls while driving, and also when using a hands free device. As long as the Supreme Court has not made any pronouncement in this respect, this instruction does not seem unwise.