Some statistics about federal motorway A61
The so-called ‘left-Rhinian motorway’ passes the urban areas of Frankfurt and Cologne / Bonn on their south-west. BAST has published a daily traffic volume of about 51,000 vehicles for both traffic directions at the permanent counting station at Miel. Almost 12,000 heavy lorries constitute nearly 23% of traffic on this motorway. Within the scope of this system the A61 is connected through several motorways to the Cologne Ring.
In Retrospect
The agency ‚Straßen NRW‘ (‚Roads of Nordrhein-Westfalen‘) has decided to upgrade the system, which was built in 1993, with new LED technology. The existing communication technology was retained: contiguous road stations combined to ‘isles’ are connected via a 1200 baud communication protocol to a central computer over legacy cables. These AUSA – cables (‘Autobahn-Selbstwähl-Anlage’= ‘motorway self-dialing-system’) can manage long distances but only low transfer rates. Locally, within isles, road stations are interconnected via other conventional transfer methods.
Looking Forward: the New System
28 existing variable message sign bridges have been renovated and 6 new bridges have been installed. During construction stage 2 the system on A1 has been extended almost to junction Hürth. In the south, gaps have been closed where display bridges have been too far apart. Traffic data acquisition systems that were malfunctioning or consisted only of a single counting loop have been replaced by or extended to double loop systems that also measure velocity. All 10 road weather detectors have been replaced. All new variable message signs have been, like the legacy signs, equipped with roller blinds. Those have an uninterrupted power supply and are closed during power outages, emergency operation mode or other system failures. The motorway is partly a two-lane-, partly a three-lane road. Counting in the variable message signs at junction Weilerswist, 76 variable message signs type A for instructions and 42 variable message signs type B/C for danger and no-passing indications have been installed.
44 Road Stations Overall in 4 Construction Stages
By using a so-called partially integrated design, using more than one real time computer per road station was made unnecessary. All required software function groups, depending on location, were installed on a single module. The interfaces to actors and sensors on the main module have been complemented with peripheral parts. Counting in two ramp metering systems and the permanent counting station at Miel, 44 computer modules were used. The road stations are programmed according to the protocol TLS 2002 but can be upgraded to use TLS 2012. For switchings in emergency control mode the same tunnel software is employed as in several other tunnel control systems, e.g. in the Europagarten tunnel in Frankfurt and the Agnesburg tunnel where the motorway A7 ascends the Swabian Alp. Brightness control of the ramp control systems is aided by an astronomical clock which is also being employed by most brightness control systems in our tunnels. A specialty of our software is the control of the roller blind, since, combined with the LED sign, two actors have to be serviced via a single channel, as described by TLS 2002. In front of every sign of type B/C, a common roller blind is mounted; the B and C channels are coordinated by an extension to the so-called locking matrix, which prevents forbidden combinations of signs on a single bridge.
