How Much Load Can That Road Hold?

measuring road strength seasonal load restriction

Technician setting up the Benkelman Beam to measure road strength.

In spring, as temperatures begin to rise, roads start to weaken. The thawing releases water in the road, that can’t drain efficiently, if the surrounding soil remains frozen.

This reduces the road’s ability to support heavy loads, so the ministry puts seasonal load limits on certain roads, or stretches of road, for heavy vehicles. White signs are posted on the road, advising of seasonal load limits for the area. This information is also posted on DriveBC and at Commercial Vehicle Inspection Stations.

When load restrictions are in place, drivers of long haul transports, logging trucks and heavy equipment transports may be required to reduce the load they would normally plan to carry on a route. They may also choose alternate roads which have no load restrictions, if they are able to reach their destination that way.

So, how do we know how much load that road can hold? A network of strategically located Frost Probe Weather Stations is used to determine when roads begin to weaken and load restrictions are required. The ministry also uses a piece of equipment, called the Benkelman Beam. “Beaming” is done by placing a load on the road and measuring the rebound. This indicates when the road has dried enough to regain its strength, and commercial drivers can resume carrying full loads, without damaging the road.

frost profile

A Frost Profile from North Fork Road in the Grand Forks area. The numbers across the top are temperature (Celsius) and the numbers at the side are the depth (cm) below road surface. The coloured circles show the temperature of the ground at various depths. This chart indicates a trend of rising temperatures and shallower frost depths, which could eventually lead to loss of road strength.

The ministry is aware that seasonal load restrictions can cause inconvenience to commercial drivers and business. So, with assistance from our highway maintenance contractors, we continuously monitor our roads for changing conditions, and use other tools such as weather forecasts and anecdotal history. Daily monitoring enables us to remove load restrictions, as soon as conditions allow.

Load restrictions are usually in place for about six to eight weeks, to protect B.C.’s road system. Drivers who do not obey the seasonal load restrictions, may be fined.

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2 Responses to How Much Load Can That Road Hold?

  1. Michael Bingham on February 19, 2013 at 10:01 am

    We are looking at moving some heavy loads Vancouver to Calgary. Could you please provide some historical data as to when load bans are removed. Dates for the past 5 years would be appreciated. Thanks in Advance
    Michael Bingham, P.Eng

    • tranbceditor on March 14, 2013 at 4:05 pm

      Hi there Michael,

      The Ministry of Transportation has reports the most current information on load restrictions at the following website: http://www.th.gov.bc.ca/bchighways/loadrestrictions/loadrestrictions.htm. There is an option on this website to sign up for this information to be emailed directly to you.

      However, in regards to your heavy haul move from Vancouver to Calgary, in a general sense, road restrictions come off somewhere between the middle to the end of May, especially in the higher areas of the eastern end of the province. In order to obtain more accurate information, or even historic information one would need to contact the appropriate district contact for the exact route. This contact information can be found on the website mentioned above by clicking on the district area link.

      We are assuming that the move will occur along the Trans Canada Highway 1. This highway will not see road restrictions, but during the road restriction period no overload permits will be permitted along the route. In other words the road restriction is 100% of legal loads only.

      If your move is to take place on a different route between Vancouver to Calgary, some other information that you should be aware of is that (i) if there are road restrictions in effect one cannot get an overload permits; (ii) road restriction dates are not consistent across the province; and (iii) the percentages of load permitted on the road can also change throughout the road restriction period.

      Hope that this helps you and good luck in your move.

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