FWIW, I've found that most common cameras in the 720p-5MP range switch from day/color mode to night/bw mode in the range of 15-20lux.
If you want to try and maintain color images, I'd suggest general illumination of 20lux or more. If you want to get a good night time image I'd suggest general illumination of 10lux or more. Anything less than 5 lux of general illumination is unlikely to yield very usuable images.
People sometimes confuse lux readings in "open air" with minimum lux ratings on camera spec sheets (eg: a .1 lux camera). The spec-sheet reading is usually not as useful as it seems, but at the very least it is referring to the light level hitting the camera sensor.
Cameras see light reflected off objects. Object reflect a portion of the light hitting them, for people dressed in cotton clothing the reflectivity is usually around 10-20%. Light also dissipates over distance. If you have a person 100' away standing under a light that is providing 5 lux of illumination in the general scene, that person will be reflecting about .5-1lux of light back toward the camera (or in any general direction). That reflected light dissipates over distance, and the camera is not able to capture 100% of the light reaching the lens (lens quality, aperture, sensor quality, etc.).
There is no easy way to measure light reaching the camera from a given object, holding your lux meter next to the camera lens only tells you about the general illumination right at the lens. There are lots of variables, but you will end up needing ~100x the low-light spec of your camera at the target to get a "good" image.
To help complicate the lighting design, you'll find that most lamps are rated in lumens, not lux. You can't directly convert one to the other without some additional details (which are nearly impossible to get). Lumens is the *total* light output of the illuminator. Lux is the amount of light hitting a defined target area. Think of it like a maglight with an adjustable "focus". You switch the light on and the bulb lights up, it's putting out "X" lumens (lets say 500). Twisting the end of the maglight doesn't change the amount of light the bulb is producing, but it focuses that light in a spot (high LUX, maybe 500?) or in a floodlight pattern (low lux, maybe 80?). Light manufactures can't give you a lux rating because they don't know over what area/distance from the lamp you'll be measuring lux, but they can tell you the total amount of illumination produced by the bulb (lumens).
I understand the question to be "what is the recommended light level for an open air parking lot". I would encourage the member to consult with local AHJ's and state law. Depending upon the businesses directly adjacent to the parking area, the "required" light levels can vary a great deal. I am not familiar with all States or codes, but an awful lot of them have requirements all their own now. If you start there; this is what is required, then you can work backwards.
If building codes allow you to expect "x" footcandles or lumens at "y" distance. Your camera selection just easier.
ATM Litigation here is one link.
Georgia ATM Lighting Standards
Palm Springs Not sure why, but they are getting pretty common here in the south. And of course the banking industry has had them for years, mostly due to litigation.
I ran into the one in Palm Springs by accident.
I ran into a building code requirement in a city (Hollywood I think) in Fl that required CCTV to cover the entrance and exit of a parking lot for any new business. When I called to ask about the specification, what was required, the answer I got, swear to God - show us what you have in mind and if we like it we will approve it. I wound up writing their code for them.