Intense lobbying to have the road upgraded saw VicRoads reduce the speed limit to 80 kilometres an hour, Victorian Farmers Federation Manangatang branch president Brian Barry junior said.

"The road is very narrow in places, too narrow for a white line down the centre," Mr Barry said.

"The edges are crumbling, narrowing the road even further."

The road had several crests and corners, where it was too dangerous for trucks to pass each other.

"Reducing the speed won't make the road any wider, smoother or fill in any of the potholes and massive drop-offs on the edges," Mr Barry said.

Manangatang sits at the crossroads of the Mallee Highway, the main highway between Sydney and Adelaide, and Robinvale-Sea Lake Road.

Mr Barry said VicRoads had told residents they were going to strengthen the road shoulders and "smooth out a few patches.

"They aren't going to make the road fit for purpose, for the traffic it gets," Mr Barry said.

"At best, it's a patch-up job."

VicRoads gave no advance warning about the speed reduction, Mr Barry said.

Mr Barry said 260 people rallied in Manangatang, and were joined by trucking companies from the area.

"It was a massive commitment from the professional truck drivers, they have forgone a lot of money, just to be there to support us," he said.

One local freight business estimated it would cost an extra $2 per tonne to send grain to port.

The reduced speed limits would add time to trips and meant the loss of one truck movement, per fortnight.

On a harvest of 5,000 tonnes, that would equate to a loss of $10,000 per farmer.

"Every couple of bucks all adds up - you put that over a 200-500,000 tonne harvest, and that's a huge amount of money, to suck out of our little town.

"We can't pass that on; it's coming out of our pocket.

"Our area produces millions of dollars of food and fibre, grains, wool, livestock, grapes, stone fruit, almonds, vegetables, other horticulture, each year and we deserve roads that are fit for purpose."

VFF Manangatang branch treasurer Christine Plant said the road had not been properly maintained for years.

"Its current condition is because Rural Roads Vicotria has not maintained the road up to a 2019 standard," Ms Plant said.

"The decrease in speeds demonstrates that RRV has no regard or vision, which ultimately affects road safety."

She said the state government was currently spending billions of dollars on the Melbourne level crossing removal program and Metro Tunnel.

But there was little money being spent on transport infrastructure in rural Victoria.

"The people living in the north-west are Victorians too, and we deserve access to safe and 21st-century standard roads in our state."

Mildura MP Ali Cupper said she understood the government took into account the safety of the road, when reducing the speed limit.

"But this is the wrong call," Ms Cupper said.

Ms Cupper met with stakeholders in Robinvale late last year to discuss priority road projects

She also took Victorian Roads Minister Jaala Pulford on a visit to the Robinvale-Sea Lake Road:

"Our community leaders, including VFF members and representatives of Swan Hill Rural City Council expressed in good faith how much this road needed fixing.

"We did not ask for the speed to be reduced, we asked for the road to be fixed," she said.

Ms Cupper said the businesses and communities along the road were already suffering, due to the recent announcement that the Murray Basin Rail Project had run out of money.

That meant scheduled improvements to the Manangatang rail line had been paused indefinitely.

"Time is money, especially when we are talking about fresh produce and grain. Part of the reason we have seen so many more trucks on this stretch of road is because of the shocking state of the Manangatang rail line.

RRV northern regional director Brian Westley said keeping people safe was the organisation's first priority, which is why it continuously undertook regular safety inspections across the network.

"At times we may need to temporarily reduce a speed limit to increase safety until improvement works can be completed," Mr Westley said.

"We don't make that decision lightly," Mr Westley said.

The Robinvale-Sea Lake Road was included in the region's upcoming maintenance program.

"Works in the coming months will include strengthening shoulders to improve steep drop offs and rebuilding some sections of the road foundation and surface to ensure the recently reduced speed limit is restored to 100km/h."

"We're currently working to finalise plans and timeframes and will update the community."