Dangerous Slowdowns(DSD), is a product feature under the INRIX safety alerts umbrella and is intended to offer an advance warning for back-of-queue slowdowns to allow drivers to appropriately consider a potential safety event ahead of them. The product has been developed atop the rich traffic flow dataset that INRIX uses to produce segment-level speeds.

INRIX takes real-time speeds from a segment and the upstream segment to determine if there is a greater than 35 mph delta suggesting a slowdown where drivers would need to take avoidance actions. Where a qualifying difference in speeds exists, Dangerous Slowdowns are intended to describe a point in space where severe braking starts.

Further evaluation of the qualifying difference in additional speeds after the initial location, will generate DSDs. DSD generation is dependent on real-time data densities and therefore, the prevalence of DSD may differ by geographic area, time of day, and day of the week.

Q and A on Dangerous Slowdowns:

Q: What are Dangerous Conditions?
A: Dangerous conditions can be defined as the location where cars are most likely to collide due to a rapid reduction of speed or harsh breaking.

Q: Are Dangerous Slowdowns based on real-time data?
A: Yes, DSDs will be created where neighboring spatial speeds indicate a rapid drop.

Q: Are all instances of breaking a Dangerous Slowdown?
A: No, not all areas of congestion will produce a DSD. If there is a queue where speeds gradually slow over multiple segments, this may not trigger the >35 mph minimum threshold between segments and, therefore may not trigger the creation of a DSD. In this way, DSDs differ from Congestion Alerts.

Q: What are the severity thresholds for DSD?
A: (3)35-45mph; (4)45-60mph; (5)>60mph [speed drop between segment B, and the downstream segment A]

Q: Are the alerts filterable by severity?
A: Yes, each DSD is assigned a severity based on the nature of the slowdown at the end of the queue; the severity rating is based on the speed difference between segments (see above for definitions of buckets).

Q: Where are DSD published?
A: On limited access roadways in Functional Road Classes (FRCs) 1 & 2.

Q: How long does a DSD last?
A: Depends on the data the platform has available at the time. DSD can be ephemeral (1 minute) or persist for an hour. It just depends on what data we have available to consider for DSD calculation, and whether that data tips the thresholds we set.

Q: What does the DSD output look like?
A: See below for an example request and response.

Q: Is this an INRIX XD-only product?
A: Currently, yes.

Q: How often are DSDs calculated?
A: Once per minute

Q: Is there documentation for DSD?
A: Yes. The has onboarding documentation. Additional assistance can be provided by INRIX sales engineers.

Q: With the improved spatial and temporal accuracy, how can I determine where the DSD occurred on the segment?
A: Using the offset field can help you determine where the DSD occurred. See below for an example and sample syntax.

Sample DSD with no offset
Sample DSD with offset

Description: Gets Dangerous Slowdown incidents in a specified region.

GET Gets Dangerous Slowdown incidents in a specified region using api v2.


  = required
Name Located In Type Description
accesstoken Query String A valid access token provided from the GET appToken API response. Alternatively, the accesstoken can be added to the request header instead of a url parameter using format 'Authorization: Bearer'.
box Query String “box” specifies two latitude and longitude pairs (using the WGS 84 datum) that outline a bounding box. The first lat/long pair should be the northwestern most point, and the second pair the southeastern most point. Format- [lat1],[long1],[lat2],[long2]. Either box or point and radius parameters are required.
point Query String Used to select a region based on a point and radius. If used, other Location parameters cannot be used. Format- [lat],[long]. Either box or point and radius or geoId parameters are required.
radius Query Double Used to select a region based on a point and radius. If the Units parameter is set to Metric, the radius is measured in kilometers; if Units is set to US (the default), the radius is measured in miles. If used, other Location parameters cannot be used. Either box or point and radius or geoId parameters are required.
geoId Query Integer Used to select a region based on a geography. “geoid” specifies the ID of the specified geography. For more information on how to obtain the ID, see GetGeography. When using a custom GeoId (previously created with CreateGeography), the first call will create cached files. Once these have been created the call will return the correct information. Using Geographies with a large area (e.g. countries) is not recommended. Either box or point and radius or geoId parameters are required.
units Query Integer Use 0 for English units, 1 for metric. Default is 0.
accepts Header String Use application/json for json format response and application/xml for xml format resposne.


Example Get dangerous slowdowns in a box request


200 Success
      "id": "abdf5c8a-5c5e-4871-9b11-c6cf739a3f5c",
      "version": 1,
      "severity": 3,
      "speedBefore": 114,
      "speedAt": 74,
      "speedDelta": 40,
      "location": {
          "geometry": {
              "coordinates": [
              "type": "Point"
          "segment": {
              "code": "1422551945",
              "offset": 1016.60187,
              "type": "XDS"
      "schedule": {
          "occurrenceStartTimeUTC": "2023-03-13T14:33:38.598Z"
      "description": {
          "direction": "S",
          "mileMarker": null

Response Elements

Property Type Description
dangerousSlowdowns Array An array of Dangerous Slowdowns
Property Type Description
id String The unique identifier associated with the Dangerous Slowdown. The same ID value will be associated with the Dangerous Slowdown while it stays in the same location on the road. If it moves to the start of another XD segment the ID will change.
description Array The road name, direction and mile marker information.
Property Type Description
roadname String The name of the road in the local language.
direction String The directionality of the road- U = Unknown N = Northbound, S = Southbound, E = Eastbound, W = Westbound, C = Clockwise, AC = Counter-clockwise
mileMarker String The highway mile marker closest to the Dangerous Slowdown.
version String The version of the Dangerous Slowdown report.
severity Integer The severity of the Dangerous Slowdown. This value can be in the range of 3-5, with 5 indicating the highest severity. 3 - Moderate impact (35-45 mph speed delta), 4 – High impact (45-60 mph speed delta), 5 – Severe impact (more than 60 mph speed delta)
speedBefore String The speed leading up to the Dangerous Slowdown. Values are in mph or km/h depending upon the input “Units” value.
speedAt String The speed at the Dangerous Slowdown. Values are in mph or km/h depending upon the input “Units” value.
speedDelta String speedAt – speedBefore (i.e. if speedAt = 96km/h and speedBefore = 56km/h then speedDelta = 40km/h). Values are in mph or km/h depending upon the input “Units” value.
location Array The location and segment of the Dangerous Slowdown
Property Type Description
geometry Geojson The Dangerous Slowdown location defined by the longitude, latitude and bounding method
Property Type Description
latitude Long The latitude value of the bounding
longitude Long The longitude value of the bounding
type String The type of bounding used ("Point" = circle, "Box" = box)
segment Array The XD segment and offset showing the location of the Dangerous Slowdown.
Property Type Description
code String Unique identifier for the segment. The value would be the TMC code or the INRIX XD Segment ID
type String Indicates type of segment. Possible values are “TMC” and “XDS”. XDS refers to a segment type of INRIX XD segment.
offset Integer, integer Start and end offset on the segment in meters
schedule Array The time the Dangerous Slowdown was first reported.
Property Type Description
occurrenceStartTime String UTC time when the incident began.