Hallo Raghunathan,

I think greatest advantage of using 433MHz is, that you can work with very short antennas. This is especially useful for hosehold applications, etc. where big antenna constructions are not particularily useful...
But for long distance transmissions, when there can be many obstacles between emitter and reciever it's of benefit to use as low carrier frequency as possible. So, may be 433MHz is not the best choice?

Excellent error detection and correction is crucial with such project. So, increase redundance of information for the transmission path. This could be done e.g. by multi transmission of same information. If you transmit information three times you are able to correct information, if an error occured in ONE frame. If you transmit more than three frames, even more errors can be corrected. If errors detected overrange certain limit (number and duration) you can have run a 'safe routine', which stops the car e.g., may be also the motor.
A good criterium for total failing transmisson is, when frames are not congruous to each other. If you transmit five frames e.g., and in three frames an error occured, then very probably only the two remaining frames are congruous and data restauration is impossible. So, criterium for total failing transmission could be, that more non congruous frames had been recieved than congruous ones.

Additional to this increase of redundance you can further increase security of transmission by introducing plausibility checks: Succeeding control commands would only slightly change control parameters, because abrupt changes of throttle or steering e.g. would not make much sense. So, if such abrupt changes are detected, a data transmission error must have been occured. Of course, your control board should not fabricate such abrupt changing control commands, either! Your control board must only produce plausible control commands.

'Safe routine can be invoked', when so many 'total failing transmission' frames or non plausible control commands have been detected, that they can no longer be neglected.

Like Michael I would also prefer single channel transmission and use of a digital frame scheme. Then you can put whole data restoration (error detection and correction) into a small and powerful microcontroller.

Good luck,
Kai