API Reference

Authentication

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

Requests without a valid key receive a 403 Forbidden response.

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

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 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 and end points accept either coordinates ({"lat","lng"}) or a street address ({"address": "…"}).

Send a JSON body with a Content-Type: application/json header. Set geojson: true to get the route back as a map-ready GeoJSON FeatureCollection; the response also reports how many low-clearance hazards were avoided.

Body parameters

Field	Description
start required	object {"lat","lng"} or {"address": "…"}.
end required	object {"lat","lng"} or {"address": "…"}.
clearance_feet required	number Vehicle height, feet component.
clearance_inches optional	number Vehicle height, inches component.
vehicle_weight_lbs optional	number Defaults to 80000.
vehicle_length_ft optional	number Defaults to 53.
vehicle_width_ft optional	number Passed to routing if provided.
geojson optional	boolean Return the route as GeoJSON.

curl -X POST "https://lowclearancemap.com/api/saferoute" \
  -H "X-Api-Secret: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "start": {"lat": 40.7, "lng": -73.9},
    "end": {"lat": 42.36, "lng": -71.06},
    "clearance_feet": 12,
    "clearance_inches": 6,
    "geojson": true
  }'

{
  "route": { "type": "FeatureCollection", "features": [ /* … */ ] },
  "hazards_avoided": 3
}

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.

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.

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.

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.

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.

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": [ /* … */ ]
}