Central toll in Stockholm restarts with IR cameras only, 700k transponders dumped

Stockholm's central area toll (SCAT) restarted Aug 1 about 13 months after a six month trial ended and ten months after a referendum showed 52/45 percent public support. A most interesting change is that the scheme now relies entirely on video tolling - use of infrared (IR) cameras that image the rear or front of vehicles and allow quite accurate reads of license plates. Drivers whose vehicles are registered and have established payment arrangements will be directly debited, while others will have 14 days to pay before being treated as violators.

Payment is online, or at terminals or over-the-counter at local banks and convenience stores.

The tolls are levied 6:30am to 6:30pm (0630-1830) weekdays with the exception of the holiday month of July, and vary between $1.50 (Crowns or SEK10) and $3.00 (SEK20) and are levied for all passes, whether entering or leaving, across 18 highway speed toll points organized into a cordon around the central area. The toll collected from any one vehicle is however capped at $9.00 (SEK60) per day to give a break to high use vehicles.

Taxis however are subject to the toll, whereas they were exempt during the trials.

Some 80 lanes are covered with equipment mounted on gantries and poles. Extensive use was made of trussed gantries of light appearance, although the bottom half of trussed posts are sheeted to prevent pranksters or vandals climbing the gantry.

IBM and Q-Free

IBM was prime contractor for design, build, and operations using Norway-based Q-Free as subcontractor for front-end toll equipment including vehicle detector/profilers, transponders and transponder readers and IR cameras with illuminators.

Poles are used for cameras for up to 2 lane coverage, while wider roadways get a gantry for the cameras.

During the trials toll transactions were split about equally between transponder tolls and video tolls.

Project manager Birger Hook of the Swedish road administration said the equipment worked "perfectly" from the start to the finish. The higher than expected rate of capturing readable license plate images led to the decision to dump the transponders - CEN standard 5.8Mhz passive transponders which cost about $30 each, have a life limited by the battery, and like every vehicle borne item have to be packaged and delivered by the toller, and fitted to the windshield by motorists. 

ADDITION: Hook told us in a series of emails that during the trials there were 250k to 400k passes of toll points a day. Only about one in a thousand on average was unreadable. Of the half video 94% were correc tly read by the optical character recognition algorithms and 6% had to be viewed by a  human reviewer to gain the licence plate number. (ADDED 2007-08-05)

2003 system in use

Q-Free released the camera system used in Stockholm in 2003. Called a MD-1550 VRU (Video Read Unit) it works in conjunction with a laser scanner that detects and tracks vehicles moving on a multi-lane roadway below. The scanner also profiles vehicles for potentially pricing trucks higher.

Each camera has an IR illuminator mounted immediately below it and is positioned pointing 30 degrees down, producing images at about 30m (100ft) distance. Cameras are sideways aimed to produce slightly overlapping fields of view to the adjacent camera for full coverage.

The system is managed by Q-Free lane controllers, doubled for redundant backup.

Automatic license plate recognition capability, a clock and digital data certification is built into cameras, so each camera delivers time and date stamped and certificated images together with the read license plate number. Images are digitally signed to reveal tampering by staff.

Politics

The toll was successful in reducing traffic in the central area by about 20%, halving waiting time and was calculated to produce benefits well ahead of costs as well as being financially profitable with a payback period of 4 years on the initial investment.

Initiated and trialed by a left socialist government the scheme was embraced for permanent implementation by a new center right government which stressed its benefits to motorists and pledged revenues to road improvements.

TOLLROADSnews 2007-08-01