What is this road/viaduct for?

I'm curious if anybody can shed some light on a mysterious piece of railroad infrastructure. I put the post in this forum, because I'm pretty sure it is most closely attached to current CR shared assets infrastructure, though there is also a CN line right there:

http://www.bing.com/maps/?v=2&cp=r1ttz6 ... orm=LMLTCC

This is a picture in Detroit, MI, looking north along 3rd Ave, where the CN/GTW tracks (on the north) and the CR tracks (on the south) cross. There is also a viaduct in between without any tracks on it. In fact, it looks like it has always been paved for highway vehicles.

There are no supports on the span, like there are for the other two viaducts:

http://maps.google.com/maps?q=detroit&h ... .9,,0,-2.7

One block to the east, there is what looks like a driveway that goes up to the viaduct:

http://maps.google.com/maps?q=detroit&h ... 87,,0,-0.9

In the bing birds eye, you can see the road descend from track level to street level over the course of the block between 2nd and 3rd.

Any thoughts on what it was used for? Thanks for any ideas.

From the direction of the concrete, it looks like it could have been track connecting the two.

Now it could just be a maintainer's access point.

interesting if you keep following the Track West (follow track to the Left) there are a few other road crossing on Norfolk Southern that are wide enough to support a few sidings and or a small yard. I do see where the track used to come up along a building on the South side and swings down off the main line. I would suspect these Viaducts to have been small run-a-rounds or pocket yards for the locals to use or sidings that the MOW gangs stored there equipment.

The framing is too light for rail loads. It is a vehicular bridge. You can see the tight framing typical of rail bridges on the adjacent span. Through girders of that depth would need piers like the adjacent bridges and floorbeams would be 5' maximum spacing.