Dear Harini,
You wanted a draft of the letter to be issued to the employees who make arrangement for their commutation on their own. The objective of the letter is to pass on the onus of untoward or unpleasant incident to the individual involved in it. To pass on the responsibility, you need not issue the letter. Undertaking for ownership for personal arrangement can be obtained from the employee also.
Whether you issue the letter or you obtain the undertaking, the question arises is what if some untoward incident happens when the cab facility is provided by the company? Will the claims for injury or death itself be attributable to employer? If yes, then what is the procedure for claim settlement? What is the difference when a person rides on one's own and avails of company-provided cab service? Are you clear about it?
Instead of riding/driving on one's own, when one commutes as passenger, the onus of safety and security shifts to the driver of the vehicle or rider of the two-wheeler. Therefore, availing of the company-given cab facility is in the interest of the employee. This point you may communicate and end your letter there itself.
Thanks,
Dinesh Divekar