Automotive Anti Collision Device

Is there something that would make radar undesireable?

Radar is the operating system for many "anticollission devices" used in automobiles.

I am not opting for radar sensor, as it will be a costly alternative.

When asked if you have considered RAdio Detection And Ranging, you say "...it will be a costly alternative."

Is this comment a result of a systems cost survey, and subsequent survey analysis? Or, is it not one of the options offered by your instructor, and thus dismissed?

This, compliments of Wikipedia (though not mentioned herein, this quote is regarding automobiles):

"A study done in 1993 on a seventy-seven gigahertz monolithic transmitter and millimeter wave technology gave some hopeful insights on the cost-effectiveness of collision avoidance systems. "This module, due to its small size, light weight and low production costs, is a significant advance in millimeter wave technology from traditional waveguide hybrid approaches and it now makes collision avoidance radars affordable." As this study was done in 1993, it shows that collision avoidance systems, although very advanced, are not as expensive as one might perceive."

Engineering is sort of like being a detective. Look around where other people have not looked, and you may discover things no one else has discovered.

Please see www.convoysafety.com

there are hard-wired and wireless devices using soundwave sensors.

There are several inexpensive ultrasonic systems. Unless environmental factors are a problem, I would use on of them.