This code list is used in association with the Designation attribute which is present within the Special Designation Area, Special Designation Line, and Special Designation Point Feature Types in the OS NGD RAMI Collection. The code list describes the type of Special Designation.



Drainage And Flood Risk

Optional designation that provides details of areas that are susceptible to drainage and flood risk.

Emergency Services Routes

Optional designation that alerts the Works Promoter if there is a need to keep the emergency services informed of proposed works and progress.

Environmentally Sensitive Areas

Optional designation that identifies information about the local environment. This includes environmentally sensitive areas, such as sites of specific scientific interest and ancient monuments, or specially cultivated areas containing shrubs, plants or bulbs which shall be reinstated using the same or similar species.

Event Information

Indication that this Street has an event planned.

HGV Approved Routes

Optional designation that allows Works Promoters to consider the impact on HGVs of restricted traffic flow or alerts the Works Promoter that wide vehicles are commonplace.

Hazardous Materials

England & Wales definition: Inapplicable. Scotland definition: Coal tar is an example of a hazardous material; it was a by-product of coal carbonisation which was commonly mixed with bitumen to create a road paving material used extensively in the UK until the mid-1950s. The resulting admixture of Polycyclic Aromatic Hydrocarbons and Benzo(a)Pyrene is carcinogenic. It is easily identified as it is a viscous brown liquid with a distinctive organic odour. It can be exposed or disturbed when older roads are excavated / planed. While the material is classified as a hazardous substance, it can be left in situ if sufficiently capped. Any capping layer may constitute a special engineering difficulty in its own right and, as such, should also be recorded as a separate entry.

Lane Rental

Indication that Street is part of a Lane Rental scheme. Section 74A of the New Roads and Street Works Act 1991 enables highway authorities, with the approval of the Secretary of State, to charge street works undertakers a daily charge for each day during which their works occupy the highway – commonly referred to as 'lane rental' schemes.

Level Crossing Safety Zone

Optional designation and mainly created by a Railway Operator. It identifies an area around a level crossing where, if occupied to carry out works, there is a risk of traffic obstructing the crossing.

Local Considerations

Optional designation that should be used to inform the Works Promoter of any special schemes that may impact working, for example, noise levels.

Parking Bays And Restrictions

Optional designation that provides details of streets with parking meters, residents' parking bays, and parking restrictions, such as yellow lines, red routes, and other permanent parking restrictions.

Pedestrian Crossings, Traffic Signals And Traffic Sensors

Optional designation that captures streets that have signal-controlled pedestrian crossings and permanent traffic signals or any Traffic Sensors in the highway.

Pipelines And Specialist Cables

Optional designation that is created by the Local Highway Authority on behalf of the private sector oil or gas pipeline owner. This designation should be treated as a reminder to consult further, not as an absolute indicator of the nature of the pipeline or cable.

Priority Lanes

Optional designation that allows the Local Highway Authority to identify the location of bus lanes and Cycle Routes in the street.

Proposed Special Engineering Difficulty

Optional designation used to identify new streets or assets of extraordinary construction. One typical use is to identify the location of a designation during any consultation period. On conclusion of the consultation period, this feature will typically become a β€˜Special Engineering Difficulty’.

Protected Street

Statutory designation which restricts the placement of apparatus by a street works undertaker. NOTE: Protected Streets are any highway or proposed highway which is a special road (Section 16 Highways Act) or highways designed by local highways authority as a Protected Street. Streets may be designated as protected, only if they serve, or will serve, a specific strategic traffic need, with high and constant traffic flows, and there is a reasonable alternative route in which undertakers can place the equipment, which would otherwise lawfully have been placed in the protected street. This includes services to existing or proposed properties in the street, or trunk supply routes passing through the street.

Road Trees

England & Wales definition: Inapplicable. Scotland definition: These are Trees that the Roads Authority are responsible for, which grow near or within the road boundary (including the verge, footway, etc.). Undertakers are reminded to follow guidance published in the National Joint Utilities Group (NJUG) Guidelines for the Planning, Installation and Maintenance of Utility Apparatus in Proximity of Trees, and that consultation may be required with the Local Authority Tree Officer prior to excavation. Where the Roads Authority have made use of tree root barriers, these should also be recorded as a separate special engineering difficulty entry.

Service Strips

England & Wales definition: Inapplicable. Scotland definition: These are areas, usually found in housing developments, abutting shared use surfaces and should be of 2m width, where the services to the housing are located.

Special Engineering Difficulty

Special Engineering Difficulties (SED) relates to streets or parts of streets associated with structures, or streets of extraordinary construction, where works must be carefully planned and executed to avoid damage to, or failure of, the street itself or the associated structure, with attendant danger to person or property. This statutory designation that requires a Street Works Promoter to provide additional advance information to the owner of the affected asset prior to works. (Section 63 New Roads and Street Works Act 1991). Usually this is in the form of a Section and Plan but may be more detailed if the asset owner requests it. Examples of structures that may require protection include: bridges, retaining walls, cuttings and embankments, isolated structures, subways and tunnels, tramway tracks, culverts, pipelines, pylons and cables (Section 5.3.2 Street Works Code of Practice 2012).

Special Event

Optional designation that provides early awareness of special events to Work Promoters to enable them to consider any actions that they may need to take to avoid any works taking place on the street during the time(s) of the Special Event.

Speed Limits

Optional designation that provides information about the speed limit applicable for the street. Only speed limits (signed or as per the legal order) over 40mph are recorded as standard, with some Local Highways Authorities providing 30mph speed limits as well. This data is intended to be used for planning of traffic management and works safety measures.

Strategic Route

Optional designation that is used by Local Highway Authorities to identify Strategic Routes, such as the Primary Route Network. Strategic Routes are identified by the Highways Agency, TfL in London, and the South Wales Trunk Road Agent (SWTRA) and North & Mid Wales Trunk Road Agent (NMWTRA) in Wales.

Street Lighting

Optional designation that helps Works Promoters to carry out works in the evenings and at nights by providing relevant information about Street lighting. It is particularly useful for when Part night lighting where a council has a policy of turning lights off during specific hours.

Streets Subject To Early Notification Of Immediate Activities

Optional designation that enables street authorities to designate streets that are particularly vulnerable to traffic. Work Promoters are required to provide early warning of activities to the authority immediately after the activity has commenced.


Optional designation used by asset owners to identify the existence of a structure that has not been designated as an Special Engineering Difficulty (SED). In cases where this identifies a Bridge, Works Promoters should regard it as a reminder that under Section 88, they must consult the Bridge Authority prior to serving Notices.

Traffic Calming Features

England & Wales definition: Inapplicable. Scotland definition: Traffic Calming Features which include islands, build-outs, cushions, raised tables, etc. Traffic calming features must be individually recorded and must be identified by the start and end co-ordinate of each feature. However, sets of cushions grouped together across the carriageway at a single location can be considered as a single feature.

Traffic Sensitive Side Road When Temporary Traffic Control Is Employed

England & Wales definition: Inapplicable. Scotland definition: A traffic sensitivity designation will also apply to the first 50metres (or complete length, whichever is shorter) of an adjoining street that has a junction with that traffic sensitive street. This code should only be used where road works on the adjoining street could cause delays on the traffic sensitive route. For example: no purpose is served by using this designation on a one-way street leading to a traffic sensitive road, as works in the one-way street could not cause traffic to back up on to the traffic sensitive street.

Traffic Sensitive Street

Statutory designation that restricts street works to be undertaken during period of high traffic (Section 64 New Roads and Street Works Act 1991). This designation highlights that works in these situations are likely to be particularly disruptive to other road users, but it does not necessarily prevent occupation during traffic-sensitive times. See Section 5.4.2 of Street Works Code of Practice 2012 for designation criteria.

Transport Authority Critical Apparatus

Optional designation that provides details of transport authority apparatus critical to operations of that authority which if damaged or if interrupted could disrupt or temporarily stop services (for example HV cables to a rail network).

Unusual Traffic Layout

Optional designation that provides details of where the layout of existing traffic signs, road markings, studs or verge markers is not in accordance with the Traffic Signs Manual.

Winter Maintenance Routes

Optional designation that helps determine the relative importance a route is given by a Local Highway Authority for clearing and treatment during the winter months.

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