Traffic & Transport
Keeping us moving
An area that now benefits from vision, that affects us all, is transportation and traffic. Monitoring of traffic and in particular Automatic Number Plate Recognition (ANPR), has changed the face of our roads, but there has also been considerable use in railway applications.
Traffic applications are many and varied and can include ANPR, toll
booth control, multi-lane monitoring, automatic toll licence
validation, red light violation, traffic enforcement systems, vehicle
recognition and identification, vehicle occupancy and speed
monitoring. Although many will comment on speed detection,
ANPR is actually greatly increasing the effectiveness of our
homeland security with image data, networked throughout the UK,
to detect or find vehicles of interest. This wide range of applications
have been made possible by developments in lighting and lighting
control technology, the versatility in functionality and triggering
offered by modern image sensors and sophisticated software. In
particular, high dynamic range cameras are available which can
provide more than 1000x the dynamic range of conventional
sensors. These cameras can produce high quality images of moving
objects in widely varying lighting conditions, for example in the
open air where the sun may come in and out at random times,
underground car parks, tunnels or traffic monitoring at night (for
example checking registration number plates without interference
from the vehicle headlights). Cameras can accept trigger signals
from motion detectors, barriers being raised, pressure sensors etc.
A wide choice of image sensors allow the most suitable resolution to
be chosen for the application. For example, resolution choice could
be influenced by the field of view necessary, such as the number of
traffic lanes to be covered, different sizes of number plates etc. Line
scan technology is also used in vehicle inspection applications such
as high integrity under vehicle surveillance. This can be used at
airports, prisons, border control, and other high security facilities to
detect foreign objects such as explosives hidden under vehicles.
Keeping on track
There are many examples of the use of vision technology on the railways both trackside and mounted on the trains themselves, even though the operational conditions are demanding. Cameras and imaging systems can be exposed to extremes of weather, vibration and physical wear. Line scan technology is being used to inspect the rails, sleepers and ballast for early detection of failure at speeds over 100 MPH, to a resolution of 0.8mm. Used in conjunction with cutting-edge pattern recognition software, this can automate the detection of track defects to help increase the safety of the railway network in a way that was previously impossible.