A slow order is a local speed restriction on a rail

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

 line which 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 due to rail geometry defects or due to accumulations of snow.

When maintenance workers wish to work under dispatcher

Dispatcher

Dispatchers are communications personnel responsible for receiving and transmitting pure and reliable messages, tracking vehicles and equipment, and recording other important information...

 protection without a designated "window" of time where no trains are allowed to run, they typically post flags at either end of the section they will be working and a slow order is posted on the track.

Slow orders tend to disrupt timetables

Public transport timetable

A public transport timetable is a representation of public transport information to assist a passenger with planning a trip using public transport. A timetable details when vehicle will arrive and depart specified locations and may be organised for by route or for a particular stop...

 and can affect time-sensitive shipments, so railroads attempt to get them cleared as soon as safely possible.