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Glossary of Terms
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Crushed and graded particles of rock or gravel used in the manufacture of road surfacing materials to provide bulk, strength and a skid resistant surface
Anchorage
ASTM
American Standards for Testing and Materials
A general term for the material used to "glue" the mixed ingredients of a road surfacing together. On asphaltic roads it is usually a form of bitumen, sometimes with additives to give it particular properties
The part of the highway carrying vehicular traffic
Central reserve
A strip of land between the separate carriageways of a dual carriageway or motorway
Chainage
A general term for the distance along a road from a fixed reference point (often the starting point of a road), derived from the time when such distances were measured in chains. Chainage usually increases in one direction of travel and decreases in the other and is shown on motorways by marker posts placed every 100 metres at the carriageway edge. On the M62 motorway the chainage is measured in kilometres from the Liverpool end, so the numbers on the marker posts on the westbound carriageway decrease in the direction of traffic.
Contact patch
The area in which the tyre and road surface come into contact with one another
Crossfall
The transverse (sideways) slope of a carriageway or highway
Design Manual for Roads and Bridges (DMRB)
A document produced by the Highways Agency providing specific guidance, standards and specifications to be adopted in the design, management and maintenance of trunk road and motorways
DETR
The Department of Environment, Transport and the Regions. Formerly known as the Department of the Environment and Transport and the Department of Transport
Double-sided safety fence
Safety fence designed to be impacted from either sides. Typically used in central reserves, between the carriageways of a motorway or trunk road
The force resisting motion between two surfaces in contact
Friction number (FN)
A measurement of skidding resistance using the ASTM locked-wheel method
A highway drainage feature found on the major highways, to the near and / or offside of the carriageway. Link into other drainage features, such as catchpits and interceptors
The "emergency" lane to the nearside of Lane 1 of a motorway
Highways Agency
The executive agency of the Department of Environment, Transport and the Regions (DETR) responsible for the maintenance and upkeep of the English trunk road and motorway network.
Highway winter maintenance
The process of preventing the formation of frost, ice or snow on a highway surface, or removing frost, ice or snow from the road surface after its formation. Also known colloquially as gritting or salting. Winter maintenance prior to the onset of adverse conditions is known as precautionary salting or pre-salting. Winter maintenance after the onset of adverse conditions is known as post salting.
Hot-rolled asphalt (HRA)
An asphaltic road surfacing material comprising a mix of bitumen, crushed rock aggregate and filler. The material is laid by a paving machine, usually in a layer 40-50mm thick, and is compacted using road rollers while it is still hot. Pre-coated chippings are also spread and rolled into the surface while it is hot. HRA has been the standard surface course material for major roads in the UK until comparatively recently.
The nearside running lane of a motorway or dual carriageway
Load
In the context of skidding resistance measurements, this is the vertical force acting on the skidding test wheel
Longitudinal
Along the line of the road (usually in the direction of traffic)
The organisation responsible for the routine management and maintenance of a defined network of trunk roads and motorways on behalf of the Highways Agency
Marker post (MP)
A numbered post on the edge of the carriageway providing a reference point and indicating the chainage. Marker posts are usually placed at 100 metre intervals and the number on the post indicates the chainage in kilometres with the number of 100 metre sections within that kilometre, recorded underneath, eg 146 1.
Material accident
The accident that occurred at Great Heck at 0612 GMT on 28 February 2001-03-15
Material bridge
Little heck railway bridge
Material location
The general locality of the accident at Great Heck
Material section of the M62 motorway
The section of the westbound M62 motorway that immediately approaches and passes over Little Heck Railway Bridge
Material vehicle / material vehicle combination
The Land Rover being driven by Mr Hart and its trailer, loaded with a Renault Savanna estate car
Microtexture
Fine-scale asperities on the surface of the road that interact with vehicle tyres to generate friction
MSSC
Mean Summer SCRIM Coefficient. The arithmetic mean of three measurements of SCRIM coefficient made during the period May-September of the same summer. This is the reference value used to characterise roads in the UK and the basis of the Highways Agency requirements for the skidding resistance of in-service trunk roads.
Open box beam (OBB) safety fence
A trapezoidal section beam mounted onto stronger 'Z' section posts
Safety barrier installed on the edge of a bridge or on a retaining wall or similar structure where there is a vertical drop, and which may include additional protection and restraint for pedestrians and other road users
Pavement Friction Tester (PFT)
A special device for measuring skidding resistance using the ASTM trailer locked-wheel method
Permanent safety fence
A safety fence permanently installed on a road
Pre-coated chippings
Crushed rock chippings that have been covered in a thin film of bitumen. These are rolled into the surface of a hot-rolled asphalt layer while it is hot (the bitumen coating melts to bind the chippings to the surface) to provide the surfacing with skidding resistance
Remedial maintenance treatment
A treatment devised in response to a particular highway maintenance problem
Road restraint system
General name for vehicle restraint system and pedestrian restraint system used on the road
Routine maintenance work
Non-urgent, planned maintenance activities
Rumble Strip
An edge line that can be provided between hard shoulders and nearside traffic lanes of motorway carriageways which provides audible and tactile warning by the use of raised ribs (sometimes referred to as "Vibra-Line")
Running lane
A lane routinely used by vehicular traffic
An installation provided for the protection of users of the highway consisting of horizontal members mounted on vertical posts. Designed to contain certain errant vehicles within certain impact criteria
SCRIM
Sideways force Coefficient Routine Investigation Machine. This is the standard equipment for measuring skidding resistance on UK trunk roads and motorways. SCRIM is a tanker lorry fitted with a special fifth wheel that is lowered on to the wetted road surface at an angle or 20 degrees
SCRIM coefficient
A single measurement made by SCRIM after standard corrections have been applied
Sensor measured texture depth (SMTD)
A measurement of road surface texture depth using a contactless laser displacement device. Equivalent to the root mean square deviation of the amplitude of the texture about a notional datum
Single-sided safety barrier
Safety barrier designed to be impacted on one side only
Skidding resistance
A general term describing the contribution that the road makes to the frictional forces between vehicle tyres and the road in wet conditions
Slip speed
The speed at which the contact patch of a skidding tyre is sliding over the road surface (this is not necessarily the same as the vehicle speed)
Structure / highway structure
A bridge, retaining wall etc on the highway network
Surfacing, surface course or wearing course
The uppermost layer of material in the road that forms the surface on which the traffic runs
Surface profile
A general term describing the evenness of the road surface along (longitudinal profile) or across its length (transverse profile)
The feature at the end of a safety barrier
Term maintenance contractor (TMC)
The organisation appointed by the Highways Agency to undertake maintenance works on a defined network of trunk roads and motorways, following instruction from the Maintaining Agent
Texture depth
A general term describing the average depth of the texture of the road surface. It is measured either as the average depth below the highest point in the surface over a given area, or the average variation in height about a notional datum level (see also SMTD)
Traction
The force resisting motion in the direction of travel when a wheel is being braked in a locked-wheel skidding resistance test
Traffic face
The face of the safety fence or parapet closest to the traffic
Transverse
Across the centre line of the road, ie. At right angles to the direction of traffic
Transition
Connection of two safety fences of different designs and/or performances
Trunk Road Maintenance Manual (TRMM)
A document providing detailed guidance and instruction on the maintenance of trunk roads and motorways in England
System installed on the road to provide a level of containment for an errant vehicle
Vibra-Line
See "Rumble Strip"
