The government is facing increasing pressure to reduce heavy-goods traffic on the main north-south route through the Alps.
A leading environmental group has warned it will file a legal complaint if the government doesn't take action.
The non-governmental Alpine Initiative group on Monday handed in a petition calling for increased efforts to bring down the number of trucks from more than 1.2 million to 650,000 by 2009.
It said the 40,000 signatures it collected were in response to suggestions by the transport ministry that it might delay until 2018 plans to put more transalpine heavy-goods traffic onto rail.
"We want to remind the government of its responsibility," said Fabio Pedrina, president of the Alpine Initiative.
The group said the target date of 2009 was legally binding after Swiss voters approved a constitutional amendment in 1994 to force transalpine traffic onto rail.
Most trucks have been crossing the Gotthard road tunnel in central Switzerland - the main north-south thoroughfare between Germany and Italy.
The environmentalists reiterated demands for the introduction of a reservation system for trucks, a trading exchange for transit slots as well as improved rail infrastructure.
Pedrina said it was technically feasible to implement the measures and Switzerland could play a pioneering role for neighbouring France and Austria.
However, Switzerland's road haulage association has rejected the proposals, saying the measures would place an unfair burden on domestic road transport and discriminate against Swiss hauliers.
The Alpine Initiative warned it was considering a legal complaint if the government refused to take action and ensure the target date for halving the number of heavy-goods trucks crossing the Alps is not met.
"The complaint would prompt a debate in parliament about the government's transport policy. It would have to explain its position on a decision taken in a system of direct democracy," Pedrina added.
swissinfo with agencies
The Alpine Initiative group was founded in 1987 and claims to have about 50,00 members and supporters.
It aims to protect the alpine environment from increasing road traffic.
The group forced a nationwide vote on the issue, which was approved by the Swiss voters in 1994.
As a result, parliament and the government decided to introduce fees for heavy-goods vehicles, increasing the maximum weight of trucks from 28-40 tons and subsidising tickets for trucks which use rail transport.
The group also helped defeat a proposal in 2004 to build a second road tunnel through the Gotthard in central Switzerland.