Legislation
If you are a company director or manager you have a corporate responsibility for the safety of your employees and if you are unable to prove effective policy and procedure for managing that risk you could face criminal prosecution.
The Legal requirement to act had been clarified by the HSE's application of health and safety in driving at work.
The police are required to investigate fatal road incidents as unlawful killing until proved to the contrary; this is in effect a murder inquiry that could mean vehicles, documents and computers being seized. Common law claims for damages following occupational related crashes to employees are also possible. Driving at work include staff popping out to the post office in their own cars!
Download the HSE guide to driving at work