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APIs

4 min read

20 February 2024

Finding speed limit of given waypoints using HERE Location Services

finding speed limit

So, you know how Intelligent Speed Assist (ISA) became mandatory for new vehicles in the EU back in July 2022? Well, as of July 2024, it's a must-have for all new vehicles sold or registered there. Basically, ISA helps drivers stick to speed limits across different roads. With HERE ISA Map, HERE provides high-quality and fresh speed limit data with comprehensive coverage across the globe. But, ever wondered how to find the speed limit at a specific spot using HERE Location Services?

HERE Route Matching API

The HERE Route Matching API v8 lets developers match GPS traces to real roads, opening doors for all sorts of driving insights and analytics, including the speed limit. So, let's say you want to know the speed limit at a certain coordinate. You'd enter that location into the API, and voila! It'd return the speed limit for that road segment.

Request Sample

This request contains the parameters: waypoint0 and  waypoint1 as the input locations and vehicle's mode respectively. We also need to specify the attributes=SPEED_LIMITS_FCn(*) to make sure that the speed limit data is returned.

https://routematching.hereapi.com/v8/match/routelinks?
apikey=<secret>
&waypoint0=42.0272,-87.9623
&waypoint1=42.0294,-87.9652
&mode=fastest;car
&routeMatch=1
&attributes=SPEED_LIMITS_FCn(*)

For this example, we use two waypoints as an input. The more waypoints are used as inputs, the better road segment results in the response. The maximum number of waypoints is limited, however, this limit is not a fixed number but is a result of the limit for the overall processing time. waypoint0 ... waypointN is comma-separated waypoint latitude, longitude in WGS-84 degree. The coordinates may be directly followed by ;transitRadius;label;heading[;optional specifications]. For more information check the API Reference

Response Sample

The response shows the speed limit for the road segment (link) in the given coordinate is 113 km/hr or about 70 miles/hr. 

{
"response": {
"route": [
{
"mode": {
"type": "matched",
"transportModes": [
"car"
],
"trafficMode": "disabled"
},
"waypoint": [
{
"linkId": "+1249795637",
...
"attributes": {
"SPEED_LIMITS_FCN": [
{
"FROM_REF_SPEED_LIMIT": "113",
"TO_REF_SPEED_LIMIT": "0",
"SPEED_LIMIT_SOURCE": "2",
"SPEED_LIMIT_UNIT": "M"
}
]
},
...
}
],
...
}
],
...
}
}

HERE Map Attributes API

The speed limit data is retrieved from HERE Map Attribute API when attributes=... parameter is included in the request. Apart from speed limit data from SPEED_LIMITS_FCn(*) layer, there are additional layers that can be requested within the Route Matching API request (see below). To explore further details, refer to the Map attributes along the route documentation.  

ADAS_ATTRIB_FCn

Curvature, height, slope, inside-builtup

BASIC_HEIGHT_FCn

Link height

DISTANCE_MARKERS_FCn

Distance marker info, location

LANE_FCn

Lane-level guidance link connectivity info

LINK_FCn

Link connectivity info for routing, guidance

LINK_ATTRIBUTE_FCn

Basic link info for routing, map display

LINK_ATTRIBUTE2_FCn

Advanced link info for routing, map display

LINK_TMC_FCn

LINK TMC for live traffic processing

ROAD_ADMIN_FCn

Road link's administrative hierarchy, postal code

ROAD_GEOM_FCn

Road link info, geometry for map display

ROAD_NAME_FCn

Road link name

ROAD_ROUGHNESS_FCn

Classification of the road surface roughness for driver warning

ROUNDABOUT_FCn

Roundabout info

SPEED_LIMITS_FCn

Car speed limit info

SPEED_LIMITS_COND_FCn

Conditional speed limit info

SPEED_LIMITS_VAR_FCn

Variable speed sign info

TOLL_BOOTH_FCn

Toll booth info for toll calculation/optimization

TOLL_LINK_FCn

Road link toll info for toll calculation/optimization

TRAFFIC_PATTERN_FCn

Typical link speed per time of day and weekday

TRAFFIC_SIGN_FCn

Traffic sign info for driver alerts

TRUCK_SPEED_LIMITS_FCn

Truck speed limit info

TRUCK_RESTR_FCn

Truck restriction info for routing

TURN_RESTR_FCn

Turn restriction info

Closing Thought

The HERE Route Matching API isn't just about matching GPS traces to road links; it also offers all the map context necessary for safety analytics, risk assessment, cost estimations, and more. Should you have any queries along the way, feel free to join us in our Slack workspace

Resources

Portrait of Erwin Soekianto

Erwin Soekianto

Developer Evangelist

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