Name Acronym Description
Railways Incident Officer RIO

Representative of the railways sent to the site of an incident involving or impacting on the railways

Ram air turbine RAT

A small turbine that is connected to a hydraulic pump, or electrical generator, installed in an aircraft and used as a power source

Reglement International concernant le transport de marchandises Dangereuses par chemin de fer RID

European regulations concerning the international carriage of dangerous goods by rail 2015.

River left

Refers to the left side of a river looking downstream

River right

Refers to the right side of a river looking downstream

Run at caution

Train drivers are informed that there is an incident on or near the railway. The driver will reduce their speed in the area to ensure stopping safely.

Running rails

The rails that the vehicle's wheels are guided along


Identified as a curvature in the landscape formed between two areas of higher ground

Safe air

An environment where the air is breathable and will not be harmful without the use of respiratory protection. (see also clean air)

Safety of life at sea SOLAS

The International Convention for the Safety of Life at Sea (SOLAS) is an international maritime safety treaty. It ensures that ships flagged by signatory states comply with minimum safety standards in construction, equipment and operation. SOLAS in its successive forms is generally regarded as the most important of all international treaties concerning the safety of merchant vessel.

Scheduled Ancient Monument

As defined in the Ancient Monuments and Archaeological Areas Act 1979, that makes provision for the investigation, preservation and recording of matters of archaeological or historical interest

Scottish Environment Protection Agency SEPA

The Scottish Environment Protection Agency is an executive non-departmental public body of the Scottish Government. The SEPA is Scotland's environmental regulator and is responsible for the protection of the natural environment in Scotland. Its main role is to protect and improve Scotland's environment.

Sites of special scientific interest SSSI

Sites of special scientific interest (SSSI) are important sites designated and protected for being the best examples of their characteristic wildlife and geology. Many of these varied habitats have developed over hundreds of years through management practices such as grazing and forestry and, in most cases, need active management to maintain their conservation status. Also see Areas of nature conservation (ANC) and Areas of Special Scientific Interest (ASSI)

Slave control panel

Control panels of a secondary nature in building systems; they may not have the full functionality found in the master control panel

SMART motorway SMART

A section of motorway that uses active traffic management techniques to increase capacity by use of variable speed limits and hard shoulder running at busy times.

Special Area of Conservation SAC

Strictly protected sites designated under the EC Habitats Directive. Refer to

Special Protection Area SPA

Strictly protected sites classified in accordance with Article 4 of the EC Birds Directive. Refer to


A miniature explosive device used to generate mechanical force, for example ejection of aircraft components

Sternal notch

The sternal notch is a well-defined, triangular depression in the lower front of the human throat

Stoichiometric mixture

An "ideal" fuel/air mixture in which both the fuel and the oxygen in the air are completely consumed

Strategic Co-ordinating Group SCG

Multi-agency body responsible for co-ordinating the joint response to an emergency at the local strategic level

Strategic Co-ordination Centre SCC

The location at which the Strategic Co-ordinating Group meets


A thin strip of material to which the skin of the aircraft is fastened

Total Operations Processing System TOPS

A computer management system which tracks the position and status of traction units and rolling stock

Traction current

Term used for electric power supply for electric rail vehicles. Normally supplied by overhead wire or electrified rail and collected by a pantograph on the roof of the train in the former case, or by shoes attached to the bogies in the latter.