A slow order is a local speed restriction on a rail line that is set below the track's normal speed limit.
Slow orders are usually imposed by railway dispatchers for sections of track that are in some way deficient or when there is a requirement to perform maintenance on a section of railway.
Slow orders are employed whenever continuous welded rail has some sort of derail or danger condition, such as an open critical joint, joints close to a bridge or movable bridge, or issues with settling ballast. Sometimes, slow orders are imposed because of rail geometry defects or snow accumulations.
When maintenance workers wish to work under dispatcher protection without a designated "window" of time where no trains are allowed to run, they typically post flags at either end of the section on which they will be working, and a slow order is posted on the track.
In June 2022, the Coast Line between Camarillo and San Luis Obispo was subject to a slow order issued by the Union Pacific Railroad due to malfunctioning grade crossing signals. As such, Pacific Surfliner trains experienced delays of up to 30 minutes since trains were required to slow down to 20 mph at most grade crossings.