After months of pro-pipeline rallies across Alberta, a protest convoy of about 170 trucks, big and small, left Red Deer early Thursday morning for a four-day trek to Ottawa.

Convoy participants and their supporters gathered before dawn, with the temperature sitting at about –25 C. Their vehicles were dressed up in banners denouncing Prime Minister Justin Trudeau and many of his government's policies.

They want to show their opposition to the federal carbon tax and Bill C-69, federal legislation that would change the way energy projects are reviewed, as well as a host of other policies they believe are adding to the economic pain that first hit Alberta when the price of oil plummeted four years ago.

The United We Roll protest comes as lawyers for the federal government and its supporters make their case today in a Regina court on why they believe Ottawa has the legal power to impose a carbon tax on Saskatchewan.

After months of pro-pipeline rallies across Alberta, a protest convoy with about 160 trucks, big and small, left Red Deer early Thursday morning for a four-day trek to Ottawa. 2:18

Regina is the first stop planned for the convoy. Organizers plan to hold a rally at Parliament Hill when they arrive in Ottawa.

Mike Jepson, one of the lead drivers, said he hopes the convoy will grow to more than 200 trucks.

"Our point is to get our jobs back. I mean, a lot of us who work in the oil and gas industry and other industries, and Alberta's hurting. We're hurting for jobs and it shows," he said.

A prayer for the truckers and rousing chorus of Oh Canada just prior to <a href="https://twitter.com/hashtag/convoy?src=hash&ref_src=twsrc%5Etfw">#convoy</a> leaving Red Deer. Official count is 159 trucks departing for Ottawa. <a href="https://t.co/4QAWCk6dMX">pic.twitter.com/4QAWCk6dMX</a> —@TerryReithCBC

"All these trucks out here, they should be working, but they're not because of what's happening in our energy sector. So, we need to put this forward."

The group passed through Medicine Hat around 3:30 p.m. MT, with plans to arrive in Regina on Thursday evening.

RCMP counted 170 vehicles when the group departed Thursday morning and participants reported that another 20 or so joined the convoy in Medicine Hat.

Many of the trucks have banners denouncing Bill C-69, the new Impact Assessment Act, which the federal Liberals say is meant to revamp and streamline the country's system for approving industrial projects, including new oil pipelines. Opponents fear the bill will do the opposite.

The new law would lift limits on who can participate in the assessment process and create an early-phase consultation with Indigenous communities and anyone else who could be impacted by a project.

It would also set out new timelines and parameters for reviews of proposed projects and eliminate overlapping assessments that are currently required for some projects, the federal government says.

Convoy driver Mike Jepson says the point of the four-day trek to Ottawa is to raise awareness of the problems facing the oil and gas sector. (Colleen Underwood/CBC)

Protesters in the convoy are also opposed to Bill C-48, which would prohibit tankers carrying crude oil from loading or unloading at ports in northern British Columbia, formalizing a similar, voluntary ban that has been in place in the region for the past 20 years.

Opponents fear it would kill off a potential international shipping route for Canada's energy products at a time of constrained pipeline capacity for Alberta oil.

Convoy ride-along

CBC News rode along with Ralph Sinclair as he set off in the convoy.

"Away we go. This is fantastic support for the oil industry in Canada," said Sinclair, who operates a company that supplies automotive parts to many different sectors, including the oil and gas industry.

"Sales have been down considerably this year. No optimism of work coming ahead, so nobody's fixing vehicles and moving ahead with anything."

A convoy of trucks left Red Deer on Thursday, bound for Ottawa to demand the federal government do more to help the oil and gas industry in Western Canada. (Tiphanie Roquette/Radio Canada)

It's not just the oil industry that's being harmed by the downturn and the failure to build new pipeline capacity to get oilsands crude to market, Sinclair said.

"It's every industry. It trickles down."

On the road, Sinclair pointed to the parking lot of a central Alberta oilfield service's firm as an example of the hard times facing the industry.

"We're going past one of Calfrac's yards. It's right full of trucks. Normally at this time of year there's maybe a third of those trucks sitting there. Most of them are sitting there parked because they've got no work."

Convoy participant Ralph Sinclair talks to CBC News as he sets off from Red Deer for the long drive to Ottawa. (CBC)

Many of the convoy participants are sporting yellow vests, which became the symbol of a protest movement that began in France last year and was initially focused on economic injustice. Convoy organizer Glen Carritt told the Calgary Eyeopener that his movement does not share any of the racist or radical views espoused by some people who refer to themselves as yellow vesters.

"Every respectful, peaceful, non-radical Canadian is welcome to join in this rally. We have no tolerance for racism, hate or any people of that nature. That's not what this is about," he said.

"Everybody's welcome that has had any concern with the current government."

One of those sporting a yellow vest was Kevin Peters. He said came down from Fort McMurray, Alta., to join the convoy, because he wants the country to realize how much his hometown is suffering.

Kevin Peters of Fort McMurray, Alta., says the federal government is treating Western Canada disrespectfully. (CBC)

"People are losing their jobs daily," he said. "People are losing their homes, losing their businesses. Fort McMurray is almost the heart of this country when it comes to the money going to the government, and they think it's acceptable to disrespect us?

"We're worried about what our government's doing. Everyone's feeling like we've been treated unfairly. So we're convoying to Ottawa to let them know exactly how we feel."

Another convoy participant, Patrick King, said putting a tax on carbon puts Canadians at a disadvantage.

"We have the opportunities to be one of the richest countries in the world with our resources, but yet we reduce our production in oil and gas, while Saudi Arabia goes and ups their production to meet what we've reduced," he said.

"They don't have to pay carbon tax on their foreign oil coming into our country, but yet we have to pay carbon tax on our bread, on our gas, on our heat, on our bills. It's bull."

Watch the convoy roll out in the tweeted video below:

Des dizaines de camions sont partis de Red Deer direction Ottawa pour manifester contre le gouvernement Trudeau <a href="https://twitter.com/hashtag/rcab?src=hash&ref_src=twsrc%5Etfw">#rcab</a> <a href="https://t.co/378S7foCWT">pic.twitter.com/378S7foCWT</a> —@TiphanieR