Why use such big gravel on the highway?

YOU ASKED: Not sure if this is an appropriate question for the Readers' Reporter column, but every time I drive the Coquihalla in the winter I notice the rather large size of the gravel on the road, especially whenever someone passes. Why is it necessary to use such large pieces of gravel? I, like many others, have had a lot of damage done by these projectiles.

- Brian P.

OUR ANSWER: This is a great question. In fact, it's an issue that's raised by highway drivers every year, so we know there are probably dozens of readers wondering the same thing.

As it turns out, there's a good reason for the size of road abrasive used on the Coquihalla Highway during the winter.

You'll notice we used the term "abrasive" rather than gravel. That's what Blair Barr, general manager of VSA Highway Maintenance Ltd. calls the mixture of crushed gravel used on the highway.

Barr's company is contracted by the B.C. Ministry of Transportation to look after the Coquihalla from Portia to Walloper, as well as the Okanagan Connector from Merritt to the Pennask Summit.

Barr says VSA doesn't choose the size of gravel. The ministry does.

"You've got to sort and crush material to come up with the specification that they require," he said of the strict guidelines.

To do this, the company employs several gravel pits scattered along its maintenance route at which it's constantly crushing gravel.

The resulting mixture must contain a gradation of material, ranging from sand particles to chunks no larger than 16 millimetres (about half an inch). Regular screening ensures the maximum size is not exceeded, said Barr. As well, the mixture also includes about three per cent salt.

"I had one person ask me the other day why the material is all square and angular and not round," said Barr.

"(The ministry) would prefer crushed material versus round. If it was all round gravel out there, or round sand, it would be like riding on marbles."

Angular pieces stick better to the icy road, added Barr.

"It's a real challenge, actually, trying to keep sand on pavement, because the semis on the Coq blow it off really quickly," said Barr.

"It's one of the frustrations we have, as maintenance contractors, is trying to keep sand on the road for the passenger vehicles."

Of course, drivers know all too well just how easily a big rig - or even a large SUV - can turn much of that winter abrasive into projectiles that land with unforgiving precision on windshields and car hoods.

Without question, it's the downside to keeping the mountain passes safe during the worst of wintry weather.

Professional engineer Al Gaunce had some additional information on the gravel issue.

"Your answer is very correct as far as it goes, and you do identify the source of the issue - the B.C. Ministry of Transport and it's specification for the "gravel." Firstly, it is not gravel, it is crushed rock and crushed to a specification that allows up to three-quarter-inch pieces.

Crushing and screening to smaller maximum size (which would have less impact on windshields) would cost more and our taxes would need to increase to cover the extra cost. I highly suspect that those who have vehicle damage from our spec crushed rock absorb the extra cost in their deductible amount in their insurance policy when getting the windshield replaced or other repairs caused by this source.

Therefore, it would seem to me that those who are unlucky enough to have to replace a windshield are the ones to pay the extra cost of having damage causing material spread on our highways.

They pay the cost but that does not fix the problem - the problem is still there. The cost to the unlucky one doesn't end there - there is lost time waiting for the window replacement, travel to get to the glass replacement location, lost time that would have been used for something more productive etc., but it does keep our glass replacement businesses prosperous.

I suppose my point is if we call a spade by its true name here, it is the Ministry specification allowing three-quarter-inch stone which causes the damage to our vehicles. Smaller maximum size of stone would cause much less damage, if any.

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