Mobile reports can be divided into two categories:
In many cases, reports of incidents made by citizens and the police can provide significant road network monitoring information – and at a very low cost compared to other surveillance technologies. Mobile reports do not provide a continuous stream of condition data provided by other surveillance technologies, but they so provide event information at unpredictable intervals that are very useful for traffic management purposes. In particular, mobile reports are very effective for incident detection.
A number of different mobile reporting methods are used in road network operations.
Cell phones are a very effective tool for incident detection. Many regions have established an incident reporting hotline to encourage citizens to report traffic incidents. This has the advantage of low start-up costs.
The widespread use of cell phones can provide useful traffic information. Triangulation techniques can determine a vehicle’s position by measuring signals from an on-board cellular phone within the vehicle. To enable this, the cell phone needs to be communicating with more than one cell-phone cell – preferably three or more for accuracy – so that triangulation can take place. Each phone is typically identified by its electronic serial number. This concept was first tested in the Washington D.C. area in the mid 1990s. This concept is different from GPS-based AVI systems in which the GPS unit on the phone determines the location, which is then communicated from the phone to a central processing system.
Emergency Roadside Telephones (ERTs) were regularly provided prior to mobile telephones becoming widely available. ERTs still provide a valuable service where there is a low ownership of mobile telephones or a mobile-phone black spot. They provide an accurate location to the operator of where a caller is located and enable stranded motorists to call for help. More generally, they allow travellers to report incidents such as accidents or stray animals on the carriageway.
To use a call box, the motorist just needs to lift the receiver or press a key to request the services of the police or emergency services. The caller is automatically connected to a control room operator.
Advanced types of ERTs provide background noise cancellation against traffic noise, and a simple question and answer facility based around «yes» and «no» keys for the profoundly deaf and foreign travellers. The Operator has a formal list of questions that they can ask in sequence by typing in the questions. The questions appear on a small screen at the ERT and the user answers using the yes and no keys. The option to select different languages is a great advantage near ports and border crossings where there is a high percentage of foreign visitors. They also have a call-back facility that enables the operator to call the stranded motorist, with a beacon and ring tone to attract attention.
Typically, the phones are located on the side of the freeway, and are spaced at distances ranging from 0.25 miles to 0.50 miles apart. On all-purpose dual carriageway arterial roads, freeways and motorways they need to be located in pairs on either side of the road to avoid travellers being tempted to cross the road to use one.
(Figure 4.5 Call Box – Image to be provided by Barry Moore)
These are teams of trained officers who are responsible for covering a given segment of the freeway. Mobile patrols have a central part to play in road network operations, spotting debris on the road, dealing with incidents and the general public. A freeway service patrol vehicle [Figure 4.6] is typically equipped to be able to help stranded motorists and, where possible, to clear an incident site. Mobile patrols are capable not only of responding to incidents, but in some cases to perform the entire incident management process (from detection to clear-up).
Technology, in the form of secure mobile communications and hand-held tablets, provides support. TETRA mobile radio communications offer digital transmission capability whilst maintaining the advantages of a Private Mobile Radio (PMR) system. In future service patrols may have command and control capability to direct and manage the deployment of on-road resources – and the potential to set VMS and signals on location, remotely from the road side.
Figure 4.6 A Freeway Service Patrol Vehicle
A relatively new technique for collecting traffic-related information based on mobile reports is crowdsourcing – using social networks such as Facebook and Twitter. Crowdsourcing is the process of obtaining information online that is provided by a crowd of people. This method has become feasible in recent years because of the significant developments in positioning and communications technologies that are linked to mobile phones which have internet connectivity. In road transport, crowdsourcing concept can be used to collect vital travel-related information in collaboration with members of a community. One of the most famous and successful of these crowd-sourcing applications is WAZE (https://www.waze.com/) – one of the world's largest community-based traffic and navigation apps. Users of WAZE share real-time traffic information, allowing members of the on-line community to save time and fuel while travelling.
Vehicles are used to report journey times and detect traffic incidents – monitoring their progress in time and space. This can be done by either using automatic vehicle location systems or by tracking the progress of identified vehicles between known fixed points on the network. The location of the vehicle in time and space is communicated to a central computer where data from different sources is fused to determine the status of traffic flow over the transport system.
Vehicle probes can provide very useful information that other detection techniques cannot – including information on link travel times, average speeds, and origin-destination information.
Different technologies are available. These include:
Vehicle probe methods give more reliable but less dense data than crowd-sourcing, which may provide better geographical coverage. Vehicle probes are often deployed by road network operators in collaboration with the owners of vehicle fleets that regularly travel the network.