20 kms
Yes they do. Uncontrolled has no gates, and only a X sign for RR crossing. It may (or may not) have lights on a side pole.
An uncontrolled railroad crossing warning sign is typically yellow with a black symbol. The sign features a graphic of a railroad crossing and may include the words "RAILROAD CROSSING." This color combination is used to alert drivers to the potential danger of an approaching train without any control measures in place.
Active crossing. A highway-railroad grade crossing that has flashing lights with or without crossing gates is called an "active railroad crossing". This is because it is activated automatically by the approach of a train, and shut off as the train passes. In the US, there are crossings that may use flashing lights that are not activated automatically, but nearly all were retired in the US by 1990. The watchman controlled flashing light grade crossing in southern New Jersey made headlines when it was retired in 1990, as the last of its kind in the country.
railroad crossing signs are railroad crossing signs, a baby could figure that one out.
An X. Because it is a cross for the railroad crossing.
15 mph for alleys, blind uncontrolled railroad crossings and blind uncontrolled intersections
The purpose of a railroad crossing sign, is to let you know that there is a railroad coming up or that there is one right in front of you.
The Transcontinental Railroad
Be happy and think then you will get the answer
level crossing = railroad crossing
Any grade crossing that has no warning devices, signs, or anything... or even one that is malfunctioning has the train stop or slow down for it. A conductor will either get off and flag the crossing by stopping cars and letting the train through with a flag or a flare will be lit and cast into the roadway. The horn, of course, would be honked as normally.