Gates were made so that people would be forced to stop behind the crossing signal to protect them from an oncoming train. Crossing gates have their weak points too...
These were the earliest crossing gates to be invented. This particular gate as shown is white with red stripes. In the earlier days up to the 1960s, these gates used to be colored white with black stripes, as well as yellow with black stripes, which Argentina still uses Today!
You can still find hobby shops that make black and white gates, but the real ones are long gone. These gates, weren't reflective, so that's probably why they were retired. Also, the earliest gates were not motorized, which meant that a railroad employee had to stay by the crossing signals.
When the signals would begin to go off, the railroad employee would have to go out and manually crank the gates down, and then back up when the train finished. I don't know when manual gates were eliminated though. Gregg has told me that the A-gates have a different name called Wishbone gates. I don't know where to find out more information about Wishbone gates unfortunately. These types of gates are very rare to find.
Also the earliest types of gates used to be wooden, but are now aluminum. Wooden crossing gates are rare to find Today.
I found out that WCH still makes and sells wooden wishbone gates! They also make gates that fold over if there's a clearance problem such as a crossing under a bridge, building or underground.
Picture taken from East Lansing, MI
Picture taken by firstname.lastname@example.org.
Standard Aluminum/Fiberglass Gate arms.
These are the type that's out there today. These are just rectangular gates. These types of gates are made from fiberglass and Aluminum. All railroad companies make these gates. Gates nowadays are reflective so that they can be easily seen at night. Earlier types of these gates were not reflective, and those types of gates are very rare to find.
B&B ARMR Corp. Crossing Gates
These types of gates are slowly starting to show up in the United States. These types of gates are more popular in other countries. You can visit their website here. These gates are much stronger than ordinary crossing gates. They can stop a 40 MPH truck from breaking through them, although they won't protect from vehicles that stop between them.