Are there any electronics gurus here? I figure I'd ask the question before I potentially recreate the wheel.

We're going to install a crossing signal at our rail facility. Has anyone made a simple enough circuit to make it work?

Here's what I'm considering:
Railroad signals operated with 10 volt, 18 watt bulbs. To maintain the vintage look of flashing incandescent bulbs, I found a crossing flasher that will operate on 12v with a 4 amp capacity on each channel. Thus, we can use 12v automotive bulbs, 18W or less figuring a max of two bulbs per channel. This is just the component that makes them flash:
https://www.trafficlights.com/flashers/afdc2-44-dc-r/r-crossing-flasher/

I’m looking at ultrasonic proximity detector circuits that will sense when something passes by and activate a simple 555 timer circuit that will drive a relay to activate the flasher. The timer will hold the relay closed for a predetermined amount of time. We’d need a sensor on either side of the crossing. Using a timer isn’t prototypical but it will make it work. I’m considering ultrasonic so it isn’t affected by sunlight possibly triggering a false detection which is a problem with infrared detectors. Something along the line of this circuit which is about exactly what I need: https://www.jameco.com/Jameco/workshop/JamecoFavorites/proximity.html.

Power would be supplied by a car battery with a solar charger.

Has anyone done something similar and how did you do it?

This is not for a track, just a display people activate when they walk by? In that case it's easy.

Go down to the home center and buy two motion sense floodlight units. What I have in mind has two floodlight holders, one IR motion sense unit, and a base. They are very inexpensive. $8 on sale sometimes (what I paid at Menards, a local chain). You just need the motion sensor and possibly the base depending on where you mount.

The motion sense unit has 120V hot and neutral going in, and a switched hot coming out. The switching is with an actual relay so no harm will happen by paralleling the outputs provided the input is from the same feed. Mount them in an appropriate way, maybe on the crossing unit or maybe somewhere else, one for each direction. These units are adjustable for duration. At minimum they stay on a few seconds while maximum is many minutes. You can probably find an appropriate setting.

Take the combined output and use that to drive your flasher. You won't need any other timer.

On the units I bought and experimented with, they work in daylight only when the time delay is set to minimum. This is to help with aiming but once you dial out to some longer time, they will only work in the dark. But this is easily overcome. On mine, inside, on either side of the sensor, there are two clear LEDs. One flashes red when the sensor senses movement. The other LED is being used as a light sensor. Yes, you read that right. The LED is used to sense daylight. (I had to research that concept because I didn't believe it--I thought it only looked like an LED but yes, it is possible to use LEDs as a light sensor.) If yours is the same you can cover it with black paint or just snip one lead. Then the device will work day or night.

I think this is an easy, inexpensive solution to your need, if I understood it correctly.

BTW, on mine, when the sensor is first energized the output will be on for about a minute before it starts motion sensing. Should not matter since I would assume you have the thing powered the whole time you are open but in case not, bear it in mind.

I briefly considered that. You can buy just the sensor and possibly bypass the voltage supply section (no 110V available at the location). But this will be outdoors at trackside and the sensor, at least the one I have, will sense somewhat reliably at close range (I only need about 6’) but won’t trigger the relay in daylight. That’s part of the circuit’s design.

Sounds like some sort of Infared light beam trigger is needed, like is used on assembly lines and keep your home's garage door from closing on something/someone. Only other option would be a proper signal circuit with approach/island/approach circuits with the associated relays, EOR relay(flasher relay) ect. That gets a wee bit more expensive.

Well, we have 2 operating signals at our museum. However, they are indoor displays. One of my members is an electronics guy and took them on as a project. He replaced the regular bulbs with automotive LED bulbs. The flashing circuit is custom made using an arduino circuit(I'm not an electronics guy, but I do know that little bit). With the LED bulbs the lights will flash for a good 10-12hrs of an alarm system battery. It could be hooked up to a step up converter, the same system may be able to be used in a normal operation, but at this point in time we don't have a need for it. He also made an arduino that will control 2 or 3 signal heads. It is set up to automatically cycle through different signal indications, and will also have the option to manually select the colour indications for a more hands on approach for visitors.

I made a security recorder trigger years ago from scratch. Now that unit is long gone, most things work on motion detection within the video/data stream now.

Did find this...
https://www.aliexpress.com/item/4000050303270.html

Also available on Amazon for about 10 bucks. Will switch up to 6 amps with an adjustable on time. You can search "Proximity/Occupancy Sensor 12 volt" and a lot of things will turn up.

You got me rethinking the infrared sensors. Found these 12V sensors on Amazon and for the price, if they won’t work right, no big deal. https://www.amazon.com/HiLetgo-Outdoor-Automatic-Infrared-Motion/dp/B01HTC5920/ref=mp_s_a_1_6?dchild=1&keywords=12+volt+pir+sensor&qid=1594607966&sr=8-6. They are three-way adjustable and they’ll directly switch the flasher module. At 100W max, there’s plenty of headroom to drive two 18W incandescent bulbs per channel. Once we get the signal installed and wired, I’ll post a critique.

Just remember that the crossing flashers as-built are only built to handle low voltage DC power. It is definitely NOT recommended that you wire up 110 volts to the light units..

This will be all 12V, fused and regulated. It seems the hardest part is coming up with a box for the battery and electronics. The box will be in direct sun so we may have to add a thermal fan for ventilation. Or shade it with something.

Enclose it in ductwork, and paint it silver. Doubt it will heat up that much.

I would only worry about a cooling fan if its going to be flashing constantly or a high rate of use. If its only on for short periods every now and then, it should be fine in a silver colored box/case.