Most all public service bikes require a toe clip of some type.

Also required to attend most training classes. Here are some of the most common types of peddling devices used today. Most every "Police" made mountain bike know the requirement, so they usually come with the plastic toe retention device. Be aware that a regular mountain bike more than likely will be equipped with just a flat pedal. So your choice is upgrade to one of these below. All of the pedals listed are currently available at 4Bike-Police.com
and other web retailers.

Plastic toe clip

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The most basic of toe clip. Pressure of the foot keeps it on the pedal.

Plastic toe with pedal strap

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Attaches to most flat pedals and adjustment strap tightens to fit riders foot. this one is the standard with police made mountain bikes.

Steel toe clip

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Just like the plastic ones but steel usually has leather straps so they dont rip or tear through the top. Most often you see these on beginners race or triathlon bikes.

Clipped in pedal

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This type can be used as a flat pedal or with a cleat bearing shoe. A patrol bike shoe is available from Patrol Bike Systems that allows for the cleat installation.

Double sided clip

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This is the clipped in mountain bike style. Again correct shoes are required.

Power Straps

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Kind of new to the police market, these straps are self tightening and maintain a grip between the shoe and pedal.

Hold Fast Foot Retention System FRS

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New on the police bike scene is the FRS. Hand sewn in the USA and a hit at IPMBA this year. Retail for about 60.00