Debris flying from unsecured loads on Perth's freeways and highways is costing taxpayers more than $2 million each year, Main Roads says.

The amount of debris being cleared off West Australian roads has increased in recent years, the agency said, with more than 50 items collected from Perth's three freeways each month.

Tradespeople and residents moving house were the biggest offenders, with most items falling off utes, trailers and trucks, Main Roads traffic operations manager John Venables said.

"We're finding things like buckets, ladders and wheelbarrows that fall off tradies' vehicles - that's our biggest ones," he said.

"It's just enormous the number of aluminium ladders that have come off vehicles, and you wouldn't want to hit a wheelbarrow, you'd certainly come off second best.

"On weekends, we get a lot of furniture on the side of the road usually from 'do it yourself' home removalists.

"We get cupboards and tables and mattresses and things like that fall off vehicles. Bricks also, that can be quite hazardous if you hit a brick at speed."

Mr Venables blamed laziness and carelessness.

"I think it is just a bit of rushing around at work and the last thing they do is actually make sure their loads are secure," he said.

"There's a bit of laziness in it, but they get to next job and then they move on to the next job and it's just the least of their concerns.

"They don't expect it to come off, but in certain conditions it will come off."

Main Roads said the $2 million bill covered the maintenance of road verges, and did not include the cost of hiring contractors to collect and remove the debris.

"Besides the cost, [there] is the congestion on our freeway as lanes and roads are closed to pick up the debris," he said.

"The fines can be up to $1,000 for people having debris fly off their cars."

Warning over clogged up emergency lanes

The Road Safety Council of Western Australia appealed to motorists to take the time to check their loads were secure before driving.

"One only has to drive down the freeway just to see the amount of rubbish on the roads and this is just unacceptable," council chairman Murray Lampard said.

"We're talking milk crates, helmets, hardhats, piping.

"They normally always end up in the our emergency lanes. Our emergency lanes must be kept clear for emergency vehicles, particularly during peak hour traffic.

"They need to be able to get through to an incident, they don't want to be held up by rubbish and debris."

Professor Lampard highlighted peak hour chaos due to mud being spilled on the Kwinana Freeway last week, and a five-car pile up earlier this year triggered by a mattress flying off a vehicle.

"We ask everybody to make sure their loads are secure, and we're particularly asking tradespeople to make sure their tools and their implements that they have on the back of their utes, trucks and trailers are secure," he said.

"There's plenty of footage of debris such as tools flying off the backs of vehicles and seriously impacting on following traffic."