highball

A highball is a hand signal or mechanical signal authorizing a train to proceed at full speed. The term originated in railroad dispatch practice, where a raised ball (mounted on a pole or post) indicated to the locomotive engineer that the line ahead was clear and the train could accelerate to track speed without restriction.

The signal takes two main forms. The mechanical highball, now mostly historical, consists of a ball or disk mounted on a vertical arm that can be raised or lowered by the signalman. A raised position means proceed at full speed; a lowered position means stop or approach cautiously. Electric signal systems later replaced these manual installations with trackside signal lights and radio communication, but the term persisted in railroad vocabulary.

When and why the signal matters

A highball clears the right of way for the entire length of a signal block, confirming that no other trains occupy the track ahead and that switches are correctly set for the train's route. The signal must be withdrawn if conditions change: if another train enters the block, if switch positions change, or if a malfunction is detected downstream. Failure to withdraw a highball in time causes head-on collisions or rear-end impacts, making signal discipline critical to safety.

Modern freight and passenger operations use radio and wayside signal systems to transmit the equivalent permission to proceed, but dispatchers and track workers still use the word highball when authorizing movement. The phrase remains shorthand in radio communication: a dispatcher tells a waiting train crew, "You have a highball," meaning the line is clear and they may depart or accelerate as appropriate for their movement authority.

The name itself reflects the historical mechanism: the ball was raised high on its mast to be visible from a distance, catching the engineer's eye before the train reached the signal post. The practice was fast and visual, suitable for an era before electric signals and radio became standard.