We have contacted Seth Neumann at Model Railroad Control Systems and Chuck Stancil at Logic Rail Technologies.

Both have agreed for us to send our customers to them for any questions regarding Grade Crossing Controllers and how to use them.

Here is an explanation also from Jim Hinds at Richmond Controls when I had asked him how these things work.

My advice is to get a dedicated controller from someone like Chuck Stancil at Logic Rail Technologies. I haven't checked in with Chuck on this matter in a long time, but I suspect he would recommend his Grade Crossing Pro.
The following are my personal opinions --- Chuck may offer better suggestions. In selecting a controller for my own layout, I would only consider using retroreflective infrared sensors, and four of them would be needed for bi-directional protection of a grade crossing on a single track. The sensors should be far down the track to each side of the roadway, and at the edge of the roadway on each side of the road. "Far down the track" means far enough so that there is time for the system to respond and fully lower the gates before the locomotive reaches the roadway when moving at the fastest allowed speed. Think of it like this:
S1====================================S2|||||||||S3==============================================S4
where ==== represents rails and ||||||||| represents the roadway. Each 'S' is a sensor.
The logic I understand is as follows (and I believe this is all automated by the Logic Rail system): Assume you start with no train in the area, the gates up, lights off, and the system watching for something to come along. As a train approaches, the FIRST distant sensor S1 detects the train and tells the controller to start the sequence. This means flashing the lights, start the bell, slowly lower the gates, and wait for the THIRD sensor S3 (the one just across the road) to be BLOCKED to verify that the train has started crossing the road. (The Logic Rail system may use the S2 sensor where I assumed the use of the S3 sensor --- I'm not sure if it matters much.)
The System now starts watching for the THIRD sensor S3 to become UNBLOCKED signifying that the end of the train has cleared the roadway. There must be time delays included so that a very brief (1 second?) unblocking does not count. At this point after a verified unblocking of sensor S3, the system keeps the lights flashing but slowly raises the gates. When the gates are fully raised, the system stops flashing the lights and ringing the bell. The system is now watching the FOURTH (far distant) sensor S4 to verify that the train continued past it and away from the roadway. After the FOURTH sensor S4 verifies that the train has completely passed it (blocked for a while and then solidly unblocked), the system goes back into its original state of doing nothing but watching for one of the two distant sensors S1 or S4 to detect something.
A train moving in the opposite direction first activates the FOURTH sensor S4, and the system watches for the SECOND sensor S2 to be blocked and unblocked, followed by the FIRST sensor S1. Thus, all four sensors are necessary.
Comment: My personal preference is for the use of RETROREFLECTIVE INFRARED sensors. I like RETROREFLECTIVE sensors because they can be mounted between two N Scale ties, and I like INFRARED because you can't see the light. I have done this before using photocells sensitive to visible light, but that means the system can't work if the room lights are too dim. Also, a casually waved arm can interrupt the light from an overhead light fixture to the visible light sensor, tricking the system into leaping into action.
(FYI, a RETROREFLECTIVE sensor has an LED light source and a sensor very closely spaced in the same package. The expectation is that the light shoots upwards and reflects downward off the bottom of a car into the input of the detector.)
Keep in mind that my layout has never advanced far enough to actually use the Logic Rail Grade Crossing parts. Chuck is likely to have found better ways than what I described.
All kinds of confusion are possible if there are multiple tracks or if the train stops and reverses or does anything other than just continue through the area. I think the train could stop and not raise issues, but there are probably limits on reversing the direction of the train. I'll bet Chuck has experienced and dealt with these and other difficulties.
What happens if the train activates the first sensor, then pulls up short of the roadway and parks for a long time? I'm sure Chuck has an answer for that. Press 'RESET'? Apparently Chuck included a time delay for this eventuality.
More personal opinion: USE LEDs, NOT LAMPS. If you must use lamps, use only the ones that are guaranteed to never burn out under reasonable conditions. (Replacing lamps in signals on layouts is less than enjoyable.)
Jim Hinds
RICHMOND CONTROLS

And here is Chuck's reply about Jim's advice above:

Jim provided sound advice! Our Grade Crossing Pro/2 would be a great solution to go with your new crossing signals (which look awesome, by the way!).

We offer two versions: one with 4 photocells (#GCP/2) and one with 4 pairs of infrared emitters and detectors (#GCP/2-IR). Jim did a nice job of describing the differences but we still offer both so that our customers have the choice.

The controller works as Jim described and does have a timeout mechanism for the situation where a train triggers the action but then reverses direction and never reaches the grade crossing.

The board includes outputs for servo motors to move the gate arms and we sell a servo motor kit (#SERVOKIT) which includes everything needed to move a gate arm.

We also offer an optional grade crossing bell sound module which plugs onto the controller board and drives any 8 ohm speaker.

For situations where there is more than one track at the grade crossing we offer the Grade Crossing Pro/2 Expander (#GCP/2-EXP and #GCP/2-EXP-IR). It handle detection and the logic for a second track and communicates with the main board through an included cable.

Although our controller will work with bulbs or LEDs we HIGHLY recommend LEDs! Note that the LEDs must be wired with a common anode (positive).