SPAD
SPAD turns up in 2 fields: railroad, surveying. Here is what it means to the people in each one.
SPAD in railroad
An incident where a train passes a red signal without authorization.
The abbreviation for Signal Passed At Danger. It is a severe safety violation and reportable incident, primarily in British and some international railway operations, occurring when a train moves past a stop signal without explicit permission from the dispatcher. A SPAD triggers immediate investigations, drug testing, and disciplinary action.
"The driver was pulled from service pending an investigation after he had a SPAD at junction four."
Spad in surveying
A flat-headed nail with a hole, driven into mine roofs to suspend a plumb bob.
A specialized survey nail made of iron, brass, or tin with a flattened head and a small hole. It is driven into wooden plugs in the roof of an underground mine or tunnel. Surveyors hang a plumb bob string through the hole to establish an exact station point over the instrument.
"Drive a spad into that timber overhead so we can hang a string and set up the transit."