Probe Data

Crowd-sourced data has become a valuable source of information as the use of smartphones becomes widespread. Users can actively – or by default – share information gathered during their trips with traffic and travel information (and other) service providers. This type of cooperation has helped to improve the detail of digital map data and real-time traffic and incident data. (See Mobile Reports)

Vehicles are being installed with sensor technology – which can provide detailed information about their environment. Major programmes for cooperative sharing of this information among vehicles and between vehicles and road network managers are being explored in Europe, the USA, Japan, and Korea. (See Coordinated Vehicle Highway Systems)

These types of data are an important resource for road network operators – where agreements can be reached on data access and sharing. It is also effective in handling real-time disaster situations. (See Case Study: Japan Cooperative Probe Data)

There are a variety of approaches to collecting traffic data from probe vehicles in order to analyse the resulting patterns:

• some depend upon Automatic Vehicle Identification (AVI) – where short-range roadside beacons recognise passing vehicles equipped with a tag or transponder
• others use camera-based licence plate readers and associated image processing techniques
• roadside detectors may passively monitor vehicle presence by detecting any WiFi signals emitted from consumer electronics in passing vehicles
• other systems require no roadside infrastructure but rely on:
  • vehicles equipped with Automatic Vehicle Location (AVL) and global navigation satellite systems (GNSS) to report their positions in real-time
  • the passive collection of massive numbers of cell-phone locations which may involve third party collection of cell-phone data
  • crowd-sourced contributions provided by consumers who sign-up to be tracked via the GPS in their phones (often in exchange for access to high quality traffic data).

The use of probe vehicles to measure travel time reliably faces three main challenges:

• latency of communication interactions (transmission delay) – vehicles need time to reach point B before point A-to-point B travel time can be measured
• “leakage” – some vehicles that pass point A never reach point B
• sample size – there may be too few vehicles travelling on the road link being measured to accurately assess the travel time

Collecting other types of probe data will often require closer integration of sensors and data reporting within the vehicle. For example, specific on-board devices and communications protocols are necessary to enable the appropriate capture and transmission of data such as windshield wiper activity or traction control system data.