An employee on tour is on duty for the entire duration. This entitles the employee to certain additional remuneration known by various names like Traveling Allowance, Dearness Allowance for tours, Tour Allowance, etc., besides the regular salary. While on tour, the duty hours are not fixed; it may not be for 8 hours; it can be more or less.
Many organizations follow the rule that the special allowance for a tour of less than 6 hours is paid 1/4 of the allowance for the whole day, more than 6 hours is paid at 1/2 the amount, and more than 12 hours is paid for the whole day. If it is a long-duration assignment, normally the 8-hour work rule is followed, but for a tour of a couple of days, the aim is to finish the job as quickly as possible and return to the headquarters.
If the overtime rule is to be applied, then there could be controversy and confusion galore on the travel time and the personal time spent while on such an assignment.