Unusual trailer axle combination
 

The recent discussion about speccing a flatbed got me thinking about an axle configuration that I don't see too often anymore. Back in the 70's-80's I used to see Canadian trailers with a regular spread tandem and a lift axe towards the middle of the trailer (Maybe about 10+ ft from the tandem.)

Does anyone know why these fell out of favour? What's the advantage to this set-up?

Examples:
http://www.hankstruckpictures.com/pi...8/file0098.jpg
http://www.hankstruckpictures.com/pi...rabel_v_03.jpg
http://www.hankstruckpictures.com/pi...ansport_ws.jpg

I've never pulled one, and never had a chance to take a good close look at them either. But, it seems to me that the rear tandems were fixed, and the bogeys were able to carry a measure of the weight from the rear axles and make the load legal. At the time, I don't believe they recognized a ten-foot spread and allowed 20K for that axle.

In Ontario you only need 9 ft to get 22,000 lbs on a axle. A common spec was a 6' spread on the tandem and a lift 9 or 10 feet ahead. They are getting phased out because Ontario is slowly getting rid of lift axles in favour of steer axles.

ontario steerable axles are still lift axles, but only can be lifted when empty and when reversing

I suppose I could look this up somewhere, but are the steerable axles generally legal in the US?

Also, why don't people use a steerable axle on a 10' tandem spread? Woulldn't it help with tire scrub?