I suggest you check the affordable Texas Instruments Evaluation Module AWR1642BOOST which incorporates the 77- and 79-GHz FMCW TI-AWR1642, or his brother EVM system based on the TI-IWR1443 which provides elevation besides azimuth (bearing) data. Texas has some nice demos of these systems available online and, besides the software develop tools, provides browser-based GUIs for testing the system.

Radar sensors use Frequency Modulated Continuous Wave (FMCW) radar to reliably detect moving or stationary targets, including cars, trains, trucks, and cargo in extreme weather conditions. Radar-based sensors are ideal for collision avoidance on board mobile equipment such as reach sackers, forklifts, and mining vehicles or port machineries such as carriers, handlers, and shippers.

The use of ANY Radio Radiation devices limited by Law. It's possible to use only milliwatts Radiation power in allowed (by local Laws) Frequency Ranges. The RCWL-0516 3.1GHz Doppler Radar sensor is such example. It has near 5m range sensitivity without any direction selectivity.

So UltraSound sensors are more suitable for civilian uses.

I suggest you check the affordable Texas Instruments Evaluation Module AWR1642BOOST which incorporates the 77- and 79-GHz FMCW TI-AWR1642, or his brother EVM system based on the TI-IWR1443 which provides elevation besides azimuth (bearing) data. Texas has some nice demos of these systems available online and, besides the software develop tools, provides browser-based GUIs for testing the system.

This is the radar we are looking forward please let me know your comments

http://www.ti.com/tool/TIDEP-0092#descriptionArea

Is this of automotive quality?

Can this withstand different weather conditions?