API Reference

Authentication

Authenticate every request by sending your key in the X-Api-Secret HTTP header. Keys are issued per account and scoped to your plan. Keep them secret and never expose them in client-side code.

Requests without a valid key receive 403 Forbidden. A valid key calling an endpoint outside your plan also receives 403, with "code": "scope_required" in the body naming the scope you need. See Plans & access.

Lost a key? Rotate it from Account settings → API access. Keys are stored hashed, so we cannot show you an existing key again.

X-Api-Secret: YOUR_API_KEY

Base URL & requests

All endpoints are served from a single base URL over HTTPS:

https://lowclearancemap.com

Bridge lookups use GET with query-string parameters. The Safe Route endpoint uses POST with a JSON body. When a parameter value contains JSON (for example a clearance range), URL-encode it before adding it to the query string.

curl "https://lowclearancemap.com/api/all_bridges?vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

Clearance filtering

Every bridge endpoint accepts a required vehicle_clearance parameter that filters results to the structures relevant to your vehicle. It accepts two forms:

Single value

A number (in feet) representing your maximum vehicle clearance. Returns every structure at or below that height.

Min / max range

A JSON object with min and/or max keys, URL-encoded. Useful for narrowing to a band of clearances.

Add the parameter to the request URL's query string. When the value is JSON (a clearance range), URL-encode it first. Most HTTP clients and language libraries do this for you.

# add to the request URL:
?vehicle_clearance=13.5

# readable JSON value:
?vehicle_clearance={"min":10,"max":15}

# URL-encoded (what you send):
?vehicle_clearance=%7B%22min%22%3A10%2C%22max%22%3A15%7D

Structure annotations

Structures carry eight annotation fields that describe the physical form of the obstruction and how its clearance was verified against imagery. Fields that do not apply to a particular structure are returned as null, e.g. posted_raw when no height sign is posted, or clearance_max_in when the opening is uniform.

Annotations are off by default so existing integrations are unaffected. Add verbose=true to any JSON bridge endpoint (All bridges, by state, by country, by ID, within radius) to receive them.

Fields

Field	Description
structure_type	string The kind of overhead structure. One of BR bridge / overpass, TRU truss, TUN tunnel, CVB covered bridge, OBS other overhead obstruction (sign gantry, pipe rack, low cable), OTH other / unclassifiable.
carries	string What sits on top of the structure. One of ROAD, RAIL, PED pedestrian or bike only, MIX multiple or other, N/A nothing carried (tunnels, covered bridges, trusses).
clearance_var	string How clearance varies across the opening, which tells a router where the opening is lowest. One of UNI uniform, ARC arched with a higher center and lower edges, SLP sloped with one side lower than the other, STEP stepped or physically separate spans with different heights.
posted	string Y if a height sign is visible on the structure, otherwise N.
posted_raw	string The sign value exactly as posted, e.g. 12'-6" or 3.8m. Null when posted is N.
clearance_min_in	integer The controlling (lowest) clearance across the opening, in inches. This is the number a router should use.
clearance_max_in	integer The highest clearance across the opening, in inches. Only populated when clearance_var is not UNI.
confidence	string Curation confidence for the annotation. One of OK, REVISIT (queued for re-check), CANT_DETERMINE (imagery insufficient).

curl "https://lowclearancemap.com/api/bridges_by_id?structure_ids=5&verbose=true" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "bridges": [{
    "Structure_ID": 5,
    "Name": "WV61 CR72 US60 KAN R CSX",
    "Latitude": 38.3007621,
    "Longitude": -81.5564591,
    "Country": "United States",
    "State": "WV",
    "Clearance": 13.5,
    "structure_type": "BR",
    "carries": "ROAD",
    "clearance_var": "UNI",
    "posted": "Y",
    "posted_raw": "13 6",
    "clearance_min_in": 162,
    "clearance_max_in": null,
    "confidence": "OK"
  }]
}

Response format

By default, responses are JSON objects containing metadata plus a bridges array. Each bridge includes its identifier, name, coordinates, country, state and clearance. Add verbose=true to any JSON bridge endpoint to also receive the structure annotation fields.

Add geojson=true to receive a GeoJSON FeatureCollection instead. Each hazard heading becomes a LineString feature, ready to drop onto a Mapbox or Leaflet map.

{
  "type": "Feature",
  "properties": {
    "Name": "CR 1 SLS",
    "State": "WV",
    "Clearance": 13.5,
    "Feature_Type": "all_bridges"
  },
  "geometry": {
    "type": "LineString",
    "coordinates": [[-77.89, 39.38], [-77.89, 39.40]]
  }
}

Safe Route POST

Safe Route is our flagship endpoint: the routing engine behind the Low Clearance Map web app and Headroom Turn-by-Turn navigation. It runs the exact same clearance-aware routing our own products rely on.

Given a start, an end, and your vehicle’s height, plus optional weight, length and width, it returns a complete, turn-by-turn route that routes around every structure your vehicle can’t safely clear, so a driver is never sent under a too-low bridge. Start, end and stops accept either coordinates ({"lat","lng"}) or a street address ({"address": "…"}).

Send a JSON body with a Content-Type: application/json header. The response always carries two routes: fastest_route, the unconstrained route with any hazards it crosses listed, and safe_route, the route that avoids them. safe_route_found tells you whether a hazard-free route exists; when it is false the safe route is the fastest route and still carries hazards. Set geojson: true to get both routes back as a map-ready GeoJSON FeatureCollection.

Body parameters

Field	Description
start required	object {"lat","lng"} or {"address": "…"}.
end required	object {"lat","lng"} or {"address": "…"}.
stops optional	array Intermediate waypoints, visited in order. Each is {"lat","lng"} or {"address": "…"}.
clearance_feet required	number Vehicle height, feet component.
clearance_inches optional	number Vehicle height, inches component.
use_truck_routes optional	boolean Route on a commercial-truck profile that also honours weight, length and width restrictions. Defaults to false (car profile with a height constraint).
vehicle_weight_lbs optional	number Gross weight. Defaults to 80000. Used in truck mode.
vehicle_length_ft optional	number Defaults to 53. Used in truck mode.
vehicle_width_ft optional	number Passed to routing if provided. Used in truck mode.
avoid_tolls optional	boolean Avoid toll roads. Defaults to false.
avoid_highways optional	boolean Avoid controlled-access highways. Defaults to false.
geojson optional	boolean Return the routes as a GeoJSON FeatureCollection (one fastest feature, one safe feature). Defaults to false.
multiple_routes optional	boolean Also return a routes array with every candidate route considered, each hazard-annotated and flagged is_fastest_route / is_safe_route, ordered hazard-free first. Defaults to false.
speed_limits optional	boolean Also return posted speed limits along every returned route as a speed_limits array of spans (see Speed limits). Defaults to false.

geojson, multiple_routes and speed_limits may also be passed as query-string parameters (?speed_limits=true). Response keys are only added when the matching flag is on; the default response shape never changes.

Speed limits

With speed_limits: true, fastest_route, safe_route and every routes[] entry carry a speed_limits array: run-length spans of the posted limit along the route. A span applies from its start up to the next span’s start; the last span runs to the end of the route. Each span is addressed two ways so you can use whichever fits your client: start_index is the index into geometry.coordinates, and start_m is the distance from the start of the route in metres, which keeps working if you resample or densify the geometry.

speed_mps is always metres per second so you can display mph or km/h as you like; unit reports the unit the limit is posted in when the routing engine knows it and is null otherwise. A span with speed_mps: null means the limit is unknown for that stretch (or unlimited: true where no limit applies). Routes served by the exclusion-routing fallback have no limit data and return an empty array.

curl -X POST "https://lowclearancemap.com/api/saferoute" \
  -H "X-Api-Secret: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "start": {"lat": 40.7128, "lng": -74.0060},
    "end": {"address": "Boston, MA"},
    "clearance_feet": 13,
    "clearance_inches": 6,
    "use_truck_routes": true,
    "vehicle_weight_lbs": 80000,
    "vehicle_length_ft": 53,
    "speed_limits": true
  }'

{
  "status": "ok",
  "message": "Alternative safe route found",
  "safe_route_found": true,
  "routes_are_same": false,
  "metadata": {
    "vehicle_clearance_ft": 13.5,
    "use_truck_routes": true,
    "vehicle_weight_lbs": 80000,
    "vehicle_length_ft": 53,
    "avoid_tolls": false,
    "avoid_highways": false,
    "route_distance_miles": 190.4,
    "is_long_route": false,
    "closure_aware": false,
    "speed_limits": true
  },
  "fastest_route": {
    "geometry": {
      "type": "LineString",
      "coordinates": [[-74.006, 40.7128], …]
    },
    "distance_m": 346210,
    "distance_miles": 215.13,
    "distance_km": 346.21,
    "duration_s": 13980,
    "hazards": [ {
      "lat": 41.2034, "lng": -73.1187,
      "name": "Elm St Underpass",
      "clearance": 11.5,
      "distance_m": 52340, "distance_km": 52.3
    } ],
    "hazards_count": 1,
    "turns": [ {
      "instruction": "Turn right onto Main St",
      "direction": "right",
      "name": "Main St",
      "distance": 812.4, "duration": 95,
      "location": [-74.001, 40.72],
      "bearing": 87,
      "intersection_type": "traffic_signal"
    }, … ],
    "speed_limits": [
      { "start_index": 0, "start_m": 0.0,
        "speed_mps": 11.176, "unit": null,
        "unlimited": false },
      { "start_index": 58, "start_m": 2054.0,
        "speed_mps": 24.587, "unit": null,
        "unlimited": false },
      …
    ]
  },
  "safe_route": {
    /* same fields as fastest_route, plus: */
    "hazards_count": 0,
    "is_same_as_fastest": false
  }
}

{
  "start_index": 58,    /* into geometry.coordinates */
  "start_m": 2054.0,    /* metres from route start */
  "speed_mps": 24.587,  /* m/s; null = unknown */
  "unit": "mph",        /* "mph" | "km/h" | null */
  "unlimited": false    /* true = no limit applies */
}

Check Route POST

Already have a route? Check Route audits a route you already have (for example the geometry returned by Google Maps, HERE, or Mapbox Directions) against your vehicle’s clearance, and tells you whether it is safe. If it isn’t, every low-clearance structure that lies on the route is listed.

Unlike Safe Route, this endpoint does not build a route or suggest an alternative; it only validates the geometry you supply. Use Safe Route to generate a clearance-aware route; use Check Route to verify a route that came from somewhere else.

Send a JSON body with a Content-Type: application/json header. The route geometry goes in route and may be an encoded polyline (Google / Mapbox, precision 5 or 6), a HERE flexible polyline, a GeoJSON LineString, a list of [lng, lat] pairs, or a list of {"lat","lng"} objects. A bridge is only flagged when the route actually travels through it in a hazardous direction.

Body parameters

Field	Description
route required	string | array | object The route geometry to audit. Aliases geometry, polyline, linestring, coordinates are also accepted.
geometry_format optional	string auto (default), polyline, polyline6, flexible, geojson, or coordinates. auto tries standard polyline, then precision 6, then HERE flexible.
coordinate_order optional	string Order of raw numeric pairs: lnglat (default, GeoJSON) or latlng.
clearance_feet required	number Vehicle height, feet component (combine with clearance_inches).
clearance_inches optional	number Vehicle height, inches component.
vehicle_clearance optional	number Vehicle height in decimal feet, an alternative to clearance_feet/clearance_inches.
on_route_m optional	number How close (meters) a structure must be to count as on-route. Defaults to 25.
heading_tol optional	number Travel-heading match tolerance in degrees. Defaults to 20.

curl -X POST "https://lowclearancemap.com/api/check_route" \
  -H "X-Api-Secret: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "route": "izpdFn~xtMhA}A",
    "geometry_format": "polyline",
    "clearance_feet": 11,
    "clearance_inches": 6
  }'

{
  "status": "ok",
  "safe": false,
  "vehicle_clearance_ft": 11.5,
  "route_points": 182,
  "hazard_count": 1,
  "hazards": [ {
    "structure_id": "15999",
    "name": "Main St Underpass",
    "lat": 34.052235, "lng": -118.243683,
    "clearance": 10.5,
    "state": "CA", "country": "USA",
    "distance_m": 1200, "distance_km": 1.2
  } ],
  "message": "Route is NOT safe: 1 low-clearance hazard(s) detected for a 11.5 ft vehicle."
}

All bridges GET

Returns every structure in the database that matches the supplied clearance filter.

Query parameters

Parameter	Description
vehicle_clearance required	number | json Maximum vehicle clearance, or a URL-encoded {"min","max"} range. See Clearance filtering.
geojson optional	boolean Set to true for GeoJSON output. Defaults to false.
verbose optional	boolean Set to true to include the eight structure annotation fields on each bridge. Works with both JSON and GeoJSON output. Defaults to false.

curl "https://lowclearancemap.com/api/all_bridges?vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "number_of_bridges": 2,
  "vehicle_clearance": { "max_clearance": 13.5 },
  "bridges": [
    { "Name": "Bridge 1", "Latitude": 34.0522,
      "Longitude": -118.2437, "Clearance": 13.5 }
  ]
}

Bridges by state GET

Returns low-clearance structures in one or more U.S. states (or U.K./Canadian regions), filtered by clearance.

Query parameters

Parameter	Description
states required	string Comma-separated state/region codes, e.g. CA,NY.
vehicle_clearance required	number | json See Clearance filtering.
geojson optional	boolean Set to true for GeoJSON output.
verbose optional	boolean Set to true to include the eight structure annotation fields on each bridge. Works with both JSON and GeoJSON output. Defaults to false.

curl "https://lowclearancemap.com/api/bridges_by_state?states=CA,NY&vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "states_given": ["CA", "NY"],
  "number_of_bridges": 2,
  "bridges": [
    { "Name": "Bridge 1", "Clearance": 13.5 },
    { "Name": "Bridge 2", "Clearance": 13.0 }
  ]
}

Bridges by country GET

Returns low-clearance structures in one or more countries, filtered by clearance.

Query parameters

Parameter	Description
countries required	string Comma-separated country names, e.g. United States,Canada.
vehicle_clearance required	number | json See Clearance filtering.
geojson optional	boolean Set to true for GeoJSON output.
verbose optional	boolean Set to true to include the eight structure annotation fields on each bridge. Works with both JSON and GeoJSON output. Defaults to false.

curl "https://lowclearancemap.com/api/bridges_by_country?countries=United%20States,Canada&vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "countries_given": ["United States", "Canada"],
  "number_of_bridges": 2,
  "bridges": [ /* … */ ]
}

Bridges by ID GET

Looks up specific structures by their Structure_ID. Pass IDs as a comma-separated list, or repeat the parameter. Unknown IDs are returned in an invalid_ids array.

Query parameters

Parameter	Description
structure_ids required	string | array e.g. 1799,15999 or repeated structure_ids=1799&structure_ids=15999.
geojson optional	boolean Set to true for GeoJSON output.
verbose optional	boolean Set to true to include the eight structure annotation fields on each bridge. Works with both JSON and GeoJSON output. Defaults to false.

curl "https://lowclearancemap.com/api/bridges_by_id?structure_ids=1799,15999,16002" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "number_of_bridges": 2,
  "bridges": [ /* … */ ],
  "invalid_ids": ["16002"]
}

Bridges within radius GET

Returns structures within a given radius of a point, filtered by clearance.

Query parameters

Parameter	Description
latitude required	number Latitude of the center point.
longitude required	number Longitude of the center point.
radius required	number Search radius in kilometers.
vehicle_clearance required	number | json See Clearance filtering.
geojson optional	boolean Set to true for GeoJSON output.
verbose optional	boolean Set to true to include the eight structure annotation fields on each bridge. Works with both JSON and GeoJSON output. Defaults to false.

curl "https://lowclearancemap.com/api/bridges_within_radius?latitude=34.0522&longitude=-118.2437&radius=10&vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "center": [34.0522, -118.2437],
  "radius": 10,
  "number_of_bridges": 1,
  "bridges": [ /* … */ ]
}

Bridges along a route GET

Returns structures that fall on a route between two points, plus those within ~50 miles of the route corridor. The response separates the two sets.

Query parameters

Parameter	Description
start_latitude required	number Latitude of the route start.
start_longitude required	number Longitude of the route start.
end_latitude required	number Latitude of the route end.
end_longitude required	number Longitude of the route end.
vehicle_clearance required	number | json See Clearance filtering.
geojson optional	boolean Set to true for GeoJSON output.

curl "https://lowclearancemap.com/api/bridges_along_route?start_latitude=34.0522&start_longitude=-118.2437&end_latitude=36.1699&end_longitude=-115.1398&vehicle_clearance=13.5" \
  -H "X-Api-Secret: YOUR_API_KEY"

{
  "number_of_bridges_on_route": 1,
  "number_of_bridges_50_miles_along_route": 1,
  "bridges_on_route": [ /* … */ ],
  "bridges_50miles_along_route": [ /* … */ ]
}