Finding speed limit of given waypoints using HERE Location Services

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.  

Closing Thought

Resources

• HERE ISA Map 
• HERE Route Matching API
• HERE Route Matching API Reference
• HERE Route Matching API - Map Attributes Along The Route
• HERE Map Attributes API - Layers