Advocacy & Safety - Beware multi-trailer big rigs.

--- One of the guys at church reported this episode which happened on a rural road with blind curves. He was bicycling on the right side of a long right curve in the road and was passed by a truck with two flatbed trailers. The truck driver steered his cab to give the cyclist room, but as the truck rounded the curve, the rearmost wheels on the last trailer (naturally) drifted over to the inside of the curve and forced the cyclist off the road. (No injuries)
Truck drivers have no control over the natural path of the rear wheels of those flatbed trailers while rounding a curve.

actually, they have alot of control over where they go, and they should be making sure the entire vehicle avoids running into things. not just the front. :rolleyes:

This can be a problem, particularly in states like Oregon, which permit triple trailers.

I've never seen a double flatbed, plenty of double trailers though. What kind of road was this, some roads have length, width, and or weight restrictions. I try to avoid two lane roads that have a high truck volume with no shoulders, theres only so much space and they have much longer reaction times if they can't pass you.

ive had single trailer emis hang back and wait till it was damn sure safe to pass me in one case for 2 miles. Soon as i found a safe place to do so i pulled off the road and waved him by. He apreciated that waved and smiled. Remember even the best truck driver could have troubles passing you in a safe manner.

The freight companies are just trying to conserve resources--and make more money--by running these long combinations, but the driver must be a fool.

Drivers are instructed to steer the wheels of the trailer in the corners not the tractor. The driver should have a mental image of exactly where the wheels of the trailer are when he navigates a corner.

As the combination vehicle moved to the left to pass the rider and then back to the right there would have been a whip effect as energy was concentrated at the tail of the final trailer.

http://www.lowestpricetrafficschool.com/handbooks/images/7/fig6-1.gif

It seems that they will put anyone behind the wheel of an 80,000 lbs vehicle these days.

actually, they have alot of control over where they go, and they should be making sure the entire vehicle avoids running into things. not just the front. :rolleyes:

You'd be very surprised how many otherwise intelligent people and drivers cannot grasp the concept of vehicle pivot points, particularly in articulated vehicles such as standard rigs or the dual-trailer variant mentioned.

Most people can't grasp the idea with a simple automobile for that matter - watch a few people parallel park without oversteering and running their rear wheels into the curb. One can plan beforehand at what angles to take a vehicle into such a space as to avoid this, yet you hardly see anyone do so.

Same thing happens with the dual trailer rig - the last wheel follows the innermost path of the turn. Don't believe me? Try it yourself with a toy (1:64) Majorette dual-trailer truck.

Take care,

-Kurt

What the op is talking about is called a pup. Typically when a semi tractor pulls 2 trailers the one furthest back is the pup & the trailers are not as long as a standard lenght trailer is. Most standard trailers are about 53' long. As far as I know, with out special permits, a semi can not have 2 standard lenght trailers pulled by the same tractor in any state. Yes there are lenght & weight limits, but if the trucking company has the permits ahead of time to allow extra weights & lenghts for specialized hauling then anything is possible.

actually, they have alot of control over where they go, and they should be making sure the entire vehicle avoids running into things. not just the front. :rolleyes:

I agree, they have 100% control over where they go -- if they're trained properly. I learned to drive a tandem at 16 :o and though it takes a little more planning, it's not really that hard. I even learned how to back 'em up without jackknifing (double-jackknifing). To say you have "no control" is to be lazy or ignorant. The driver has responsibility for his rig.