There could be no bus service in Gatineau as of 4:00 a.m. Friday.

The Société de Transport de l'Outaouais (STO) says they have been served with 72-hours notice of a strike.

The notice by the Syndicat uni du transport local 591 was served Tuesday morning, less than a day after the Canada Industrial Relations Board ruled STO service was non-essential.

STO President Gilles Carpentier said in a statement the STO is "dismayed the union is taking the population hostage," and reiterated the STO's claim that a strike would negatively impact public health and safety. That argument was rejected by the CIRB.

Carpentier says the STO remains willing to negotiate in good faith.

The union is planning to meet Wednesday, to discuss its next moves. Bus drivers and maintenance workers represented by the union have been without a contract for two years.

The STO says, unless a deal is reached, no regular transit service including student service will be available starting Friday morning. Paratransit service will not be affected by a strike, and will remain available.

Beyond the Outaouais, STO buses also serve parts of downtown Ottawa.

In the winter of 2008-09, OC Transpo drivers and maintenance workers were off the job for 51 days after voting overwhelmingly in favour of a strike, leaving many residents scrambling to find alternative ways to get to work or school.