The government is facing heavy pressure to relax restrictions on traffic using the Gotthard tunnel.
Motoring associations are to push for an end to chronic traffic congestion in the tunnel during round-table discussions with federal authorities on Thursday.
Drivers and road haulers associations are renewing calls for the government to abandon the alternating one-way system for trucks through the Gotthard, which they say has caused chaos on the main transalpine route through central Switzerland.
The system was introduced last December in the wake of a fatal fire, which was triggered by a head-on collision between two trucks. Eleven people died in the blaze.
Federal and cantonal transport groups, political parties and motoring associations are taking part in the talks, which are to focus on short term measures to improve conditions for drivers using the tunnel.
"There are about 20,000 people using the tunnel every day, and the current situation is very problematic for them," said Rudolph Zumbühl, head of economic affairs at the motoring association, the Touring Club of Switzerland (TCS).
"There is no infrastructure to cope with the high number of stationary lorries that are waiting to enter the tunnel, which also pose a safety risk," he told swissinfo.
The government last month defended the restrictions, saying the current limit of 3,500 trucks per day was introduced to smooth traffic on the main motorway, and for the customs authorities at the borders to Germany and Italy respectively.
Thursday's talks come a day after Italian truck drivers blocked the southern entrance of the tunnel in Chiasso during morning rush hour in protest at excessive congestion.
"The current situation is just not viable long-term," Zumbühl told swissinfo. "The only answer is to build a second tube within the tunnel to cope with the traffic."
Rail ferry in the pipeline
Long-term, the government says its plans to build a rail ferry for freight transport through the tunnel. But the Swiss transport minister, Moritz Leuenberger, has stressed that the current system will stay in place for the time being for safety reasons.
"There's the possibility that some short term measures will be put in place during the talks, but that really remains to be seen," Hugo Schittenhelm, a spokesman for the Transport Ministry, told swissinfo.
"We'll be putting forward our own proposals regarding the current one-way system and we'll certainly take into consideration what different groups have to say," he added.
Meanwhile, Hans Werder, the general secretary of the Swiss transport ministry, last week said he was also considering introducing a system that required truck drivers to book their journey through the tunnel in advance.
A survey of European tunnel safety has described conditions in Gotthard tunnel as "adequate". The survey, jointly conducted by 14 European motoring associations, said safety installations were of a high-level, but that problems persisted because of excessive traffic.
"There's a lot of noise and too much congestion inside the tunnel," Erich Schwizer, a spokesman for TCS, which took part in the survey, told swissinfo. "Long-term, the only really safe solution is to build a second tube in the tunnel so that cars don't have to circulate alongside buses and trucks."
Schwizer said a new ventilation system, to be build later this year, would further improve the Gotthard's safety ranking.
The survey voiced concern about the safety of the San Salvotore tunnel near Lugano, built 35 years ago, which has had to deal with heavy traffic owing to congestion and closures in the Gotthard and San Bernadino tunnels.
Signs for emergency exits, video surveillance cameras and improvements to the ventilation system were among the survey's most urgent recommendations for San Salvatore, whose safety measures were described as "dubious".
by Vanessa Mock