Data Sources & Provenance

Summary table

Dates are when the extract was taken for CivilsRoute; the underlying datasets are refreshed on their own schedules (the NH Network Model, for example, updates daily). Every dataset is released under the Open Government Licence v3.0 — the region-boundary layer carries an additional OS attribution requirement, shown in the Licence column below.

Dates are shown to the precision recorded at the time of extraction. NH Structures was obtained via an FOI/EIR request rather than an open-data portal, so — consistent with National Highways' usual response practice — it's dated to calendar year only; Marker Posts predates our current extraction-logging convention and is likewise shown to year precision. Neither reflects a gap in the underlying records. *National Cycle Network: Sustrans (now Walk Wheel Cycle Trust) publishes this data under OGL v3.0, but asks that re-publication be confirmed with them directly — see the National Cycle Network section. A&E Hospitals and Police Force HQs are compiled point lists, not a single open-data extract — see the note below before relying on them.

NH Structures

*_Structures.csv — National Highways' inventory of structures on the Strategic Road Network: overbridges, underbridges, footbridges, retaining walls, culverts, sign and signal gantries, CCTV masts and similar. Each record carries a structure reference (STR_…), type and subtype, the road, the maintenance area and a region tag.

Detailed inspection and assessment records are not open data — those are obtained from National Highways under a project information protocol. This layer is asset locations and classifications only.

Road Network

network_*.json — the Network Model (Public): a link-and-node model of England's Strategic Road Network with road numbers, carriageway form, direction, lane counts, junction references and a What3Words tag per link. It is the geometry behind the "Road Network (Lines)" layer.

Red Line Boundary

boundary_*.json — the RedLine Outline (Operational Highway Boundary): the polyline outline of the land that belongs to the highway for the whole SRN. It is the geometry behind the "Red Line Boundary" layer.

Marker Posts

*_markerposts.csv — Strategic Road Network Marker Posts: the driver location signs installed along the SRN, nominally at 100 m intervals, each with a post reference (P…), section name, road, direction and maintenance area. It is the "Marker Posts (100m)" layer.

Coverage is roughly 100% of motorways, ~55% of dual-carriageway A-roads and ~25% of single-carriageway A-roads — driver location signs were rolled out mainly on high-speed roads, so a single-carriageway trunk A-road legitimately shows no marker posts.

Water Quality Priority Locations

outfalls.json — National Highways' Water Quality Plan 2030 confirmed high priority locations: the outfalls and soakaways confirmed as priorities for new or upgraded treatment by the end of the 2030/31 financial year. These are drawn from National Highways' wider assessment of 1,236 outfalls and soakaways judged potentially at high risk of polluting the environment around the network, of which up to around 250 are ultimately expected to need new or upgraded treatment — the current list is that flagged subset, not the full 1,236-location inventory. Each point carries an asset reference, the road, the receiving waterbody, a delivery status, and a mitigation-scope status (WQP_Mitigation). This is a water-quality mitigation scheme tracker, not a general drainage asset inventory; the much larger drainage-and-geotechnical asset dataset National Highways holds internally (condition scores, pipework, cuttings and embankments) is a separate dataset, obtained separately and not yet part of any CivilsRoute layer. The list has changed substantially since the October 2025 publication, not simply grown: 108 of the original 182 locations carry over unchanged, 74 were removed, and 142 further locations were newly identified or reprioritised in, bringing the current total to 250. National Highways' stated reasons for removal are a mix of genuine resolution — existing treatment identified, or the site already being addressed under a separate scheme — and rescoping, most commonly a location being deprioritised following further assessment, or found not to drain a highway or not to be a National Highways asset in the first place. National Highways publishes the removed/reprioritised locations as a companion list, with a reason recorded against each one. This is the "Drainage Constraints (Outfalls)" layer.

Refreshed 11 September 2026 to National Highways' updated publication of 250 confirmed high priority locations, replacing CivilsRoute's original extract of the October 2025 publication (182 locations).

Crash Data (STATS19)

*_crashes.csv — the Department for Transport's Road Safety Data: the statutory STATS19 record of every personal-injury road collision in Great Britain, with severity, date, road and junction detail, conditions, and vehicle/casualty counts. The CivilsRoute extract covers collision years 2020–2024. It is the "Crash Data" / STATS19 layer.

Standard STATS19 caveats apply: slight injuries are under-reported, severity reporting changed with injury-based systems around 2016–2019 (the extract keeps DfT's adjusted-severity estimates), and coordinates are approximate.

Flood Zones

flood_*.json — the Environment Agency's Flood Map for Planning, simplified to Flood Zone 2 and Flood Zone 3 polygons with a fluvial / tidal source tag (flood_zone, flood_source). It is the "Flood Zones" layer.

The Environment Agency retired the separate Flood Zone 2 and Flood Zone 3 datasets in 2025 and replaced them with a single "Flood Map for Planning — Flood Zones" product; the CivilsRoute extract preserves the FZ2 / FZ3 distinction. Flood Zones do not account for defences — always check the current EA map for a live scheme.

Habitats

habitats_*.json — Natural England's Priority Habitats Inventory (England): the spatial inventory of habitats of principal importance under Section 41 of the NERC Act 2006, mapped to polygons with a main-habitat name and code (MainHabs, HabCodes — e.g. Deciduous woodland / DWOOD). It is the "Protected Habitats" layer.

SSSI, SPA & SAC

sssi.json — Sites of Special Scientific Interest (England): land notified under the Wildlife and Countryside Act 1981 as nationally important for its wildlife, geology or landform. spa.json — Special Protection Areas (England): sites classified under the Birds Directive for rare and vulnerable birds. sac.json — Special Areas of Conservation (England): sites designated under the Habitats Regulations for habitats and species of European importance. These are the "SSSI", "Special Protection Areas" and "Special Areas of Conservation" layers.

Ancient Woodland

woodland.json — Natural England's Ancient Woodland Inventory (England): land continuously wooded since at least 1600 AD, covering Ancient Semi-Natural Woodland, Plantation on Ancient Woodland Sites and Ancient Wood Pasture. It is the "Ancient Woodland" layer.

AONB, National Parks & Scheduled Monuments

aonb.json — Areas of Outstanding Natural Beauty (England), now rebranded National Landscapes. parks.json — National Parks (England) boundaries. Both are Natural England designations, not Historic England — the in-app layer labels currently say "Historic England" for these two, which is being corrected to Natural England. monuments.json — Scheduled Monuments, from Historic England's National Heritage List for England (NHLE), which is correctly attributed to Historic England. These are the "Areas of Outstanding Beauty", "National Parks" and "Scheduled Monuments" layers.

Air Quality Management Areas (AQMA)

aqma.json — Air Quality Management Areas: the boundaries local authorities have declared under Part IV of the Environment Act 1995 where one or more national air quality objectives is not expected to be met, and which the authority must address in a formal Air Quality Action Plan. Each polygon carries a name, an AQMA reference, the declaring local authority's ONS code, and a documentation link to Defra's UK-AIR register entry for that AQMA. It is the "Air Quality Management Areas" layer.

AQMA boundaries are declared and revoked by individual local authorities on their own timescales, not on a fixed national cycle — this is a snapshot, not a live feed. Always check the relevant authority's current Air Quality Action Plan for a live scheme.

National Cycle Network

ncn.json — the National Cycle Network (Public): over 12,000 miles of signed walking, wheeling and cycling routes across the UK, with route number, surface, lighting and traffic-free/on-road status per segment. It is the "National Cycle Network" layer.

Contains Ordnance Survey data © Crown copyright and database right.

Operational-region boundaries

boundary_area_*.json — the "NH Operational Regions" overlay: one polygon for each of National Highways' seven operational regions plus London (Area 5). The shapes were reconciled against National Highways' own published regional maps (in the project's NH regions folder) and corrected using authoritative administrative boundaries.

Emergency Areas (ERAs)

eras.json — Emergency Areas (also called Emergency Refuge Areas / SOS areas): the marked refuge points on smart motorways where a hard shoulder isn't continuously available. It is the "Emergency Areas (ERAs)" layer.

The file structure (ArcGIS-style objectid/globalid fields) matches National Highways' other open-data exports, but the specific NH open-data catalogue item for this layer hasn't been individually re-confirmed for this listing — treat the exact source item as unverified until checked.

A&E Hospitals & Police Force HQs

hospitals.json — 194 major trauma centres and Type 1 A&E departments in England, with name, address and type. police.json — the 43 territorial police force headquarters of England and Wales, with name, address and phone number. These are the "A&E Trauma Hospitals" and "Police Force HQs" layers.

These two layers are curated reference lists, not an open-data extract with a licence and refresh cycle like the layers above. Hospital designations and force contact details can change — verify against the source organisation before relying on either for operational use.

Processing & regional splits

The National Highways datasets are published as single England-wide layers with no region field. CivilsRoute splits them into the seven operational regions so the app can load one region at a time. That split — and the region overlay itself — has been corrected in stages:

• England clip — the overlay polygons' generalisation crossed the England–Wales border; clipped back to the ONS England land border.
• Severn crossings — South West extended ~450 m west to cover NH's own M4 Gwent Viaduct / Gantry G8W structures and the M4 / M48 geometry that legitimately sits in Monmouthshire.
• Three boundary fixes, verified against the NH maps: east Dorset (Bournemouth / Poole / Christchurch + the A31 / A35 / A338) moved from South East to South West; Glossop / High Peak moved from North East to North West; Rugby / M6 J1 / the M45 spur moved from East Midlands to West Midlands.
• Re-split — the Road Network, Red Line Boundary and Marker Posts were re-assigned to regions against the corrected polygons, so all the datasets carve the country up the same way (marker posts by their NH maintenance-area code; network and Red Line by geometry, each feature stamped with an nh_region property).

None of this alters the source data values — only which regional file each feature lives in and, for the region polygons, their extent. The transformation scripts live in the project's tools/ folder.

Licensing & attribution

Every dataset above is published under the Open Government Licence v3.0, which permits copying, adapting and commercial use with attribution. CivilsRoute's attribution:

Contains public sector information licensed under the Open Government Licence v3.0. Data sources: National Highways; Department for Transport (STATS19); Environment Agency; Natural England; Historic England; Office for National Statistics; Sustrans (Walk Wheel Cycle Trust). Contains OS data © Crown copyright and database right 2026.

A&E Hospital and Police Force HQ locations are compiled reference lists, not licensed open data — see the note above.

CivilsRoute is a visualisation and planning aid. Every figure, boundary and asset position must be verified against the originating source and confirmed on site before it is relied on for design or construction.