Dear friends.
We researched thematic of LPR and how it work. There are 2 main features:
1. IR range. Of course, only one opportunity to make LPR is operation in IR range.
2. Synchronization between IR-illuminating device and shutter. The main point of this complex is that IR-illuminating is operating in pulse mode: IR leds make a light pulse, after that this beam reaches place of license plate, reflects from LP and returns to shutter side. Exactly at this time shutter opens and closes. Shutter speed is so high, that if there is not LP in that exact place, all picture (even in daytime) is dark. Usual camera can't reach these 2 conditions: superhigh shutter speed and synchronization between IR-leds and shutter.
In any other case on the white LP all image will be white.
We solve this problem with white LED instead of IR. We are using cameras in b/w mode, but we turn off IR-LED at all. White LED spotlight can be installed in front of LP (well working at parking), or in the side of LP on the roads (to avoid problems with drivers).
But usually for roads they used special hardware and software complex as I described below. Most part of such questions ask installers for parking zone. In this case white LED really helps.