Overtime Vs Night Stay Allowance

Dear All,
Drivers are being paid overtime. we want to introduce night stay allowance,while they are on tour/ on out station duty and have to stay at one station during night hours.
can we stop paying overtime while paying night stay allowance to drivers?
pl comments/ advice.

Overtime is payment over and above duty hours; night shift allowance is for duty hours during nights. Both are seperate heads; yes - you can stop paying overtime if there is no duty beyond official work timings.