Vehicular Sensor Networks: General Aspects and Implementation Issues - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 226

Cooperative maneuvering ( e.g., highway merging ). In this application, vehicles
calculate in real time their relative position and trajectories. Then, when a risky
situation and/or a potential collision is detected, drivers of relevant vehicles can be
promptly warned.
Cooperative tunnel safety . This application is specifically designed for road tun-
nels. It relies on the roadside infrastructure that informs vehicles about recom-
mended speed and safety distance. As a result, the safety margin is calculated on
the basis of the state and typology of the vehicle.
Hazard and incident warning . This application targets transmission of warning
messages to vehicles arriving in an area where an accident has just occurred. The mes-
sage can be issued from the roadside infrastructure or from other vehicles and may
include type of hazard, current location, and previous positions, speed, direction, etc.
Safe urban / extra urban intersections . This application requires a very precise
computation of the vehicles trajectories and local digital maps of the intersections.
The infrastructure delivers information to the vehicles to recognize dangerous situ-
ations in time [ 4 ].
Railway safety [ 40 ]. Overheated axles and locked brakes are the main immediate
causes of potential failures in railway operation. As a result of this, the axle casting
may break causing the train to derail. Furthermore, locked brakes represent poten-
tial problems, e.g., overheating releases wheel rims or may cause wheel disks to
break. Locked brakes may also result in fires leading to the formation of treadles
spots. The railway safety system application [ 40 ] can identify all bearing types and
braking systems used in international railways at speeds of up to 500 km/h and
reliably detect potential areas for failure. In addition to being competitive, the sys-
tem is modular, allowing for rapid and low-cost maintenance. The core component
of the system is an infrared optical sensor that conducts redundant row-scans of the
bogie at widths of up to 120 mm. The system has an integrated signal processor for
fast and accurate processing of measured values. The infrared sensors are designed
to be plug-in modules, integrated into a hollow sleeper, and include all the micro-
electronic components needed to process the measured values. They are precisely
positioned by pre-adjusted module frames and can be fully replaced for servicing
within just a few minutes without distorting the measurement geometry. Servicing
does not involve any adjustment whatsoever at all! The measured values are pro-
cessed and sent via a secure high-speed data transmission line to the Service &
Communication Terminal (SCT). Integrated digital electronic components perform
the task of processing the recorded thermal images as well as all the controlling
functions for the sensor module. A detailed temperature profile with 450 scanned
points per axle with a diameter of 25 cm can be recorded at train speeds of 500
km/h (this corresponds to 1,125 scanned points at 200 km/h). Built-in environmen-
tal sensors are used to take into account all the relevant vectors (e.g., moisture and
temperature) during this process. Ongoing auto-diagnostics of all system compo-
nents as well as automatic service request indicators have been included for high
reliability and economic operation.
Electronic train management system [ 41 ]. This system integrates new technology
with existing train control and operating systems providing a safety overlay, working