Bids have been submitted by Austria's Kapsch TrafficCom, Slovenian firm Cetis, and two consortia, Iskratel in conjunction with Slovak Skytoll and Telekom Slovenije together with Norway's Q-Free.

Kapsch lodged a request for review of the tender prior to the deadline for the submission of bids, on as yet unspecified grounds. All bids will be opened once the review request is decided.

"As the contracting authority we want to get a credible final decision by the competent authorities regarding the Kapsch request for review," said Bojan Banfi, who is in charge of the tender at DARS.

Banfi refused to speak about the substance of the Kapsch request, and he urged the other bidders to refrain from commenting as well.

DARS will not respond to the request, whereupon Kapsch will decide whether or not to take the case to the National Review Commission, which is in charge of resolving complaints regarding public tenders.

The e-tolling contract covers vehicles exceeding 3.5 tonnes; cars and vans will still be required to use the current system of toll stickers.

It has been years in the making, mired in complaints and accusations of heavy lobbying. The first one was issued in 2011, the second one in 2013, and the last one in July this year.

The contract does not specify the technology to be used, as long as it is in line with EU rules.

Various systems are currently in use around the world, utilising either GPS, microwave systems, vehicle licence plate identification, or RFID tags.