Hi Gary, and welcome back!
I have some information that will hopefully be useful for you.
First about the bridge at mile 176. It goes across the Wabsash River. Using the zoomed in map below, plus some interpolation from the scale, it appears that each direction is 45 feet wide (and carries two lanes of traffic).
The length of the span over the river is about 560 feet, and the length of the entire span (including the approaches) is about 1300 feet.
(Ref, you can zoom in and out to see it better: http://maps.google.com/maps?f=q&hl=en&q=lafayette,+in&layer=&ie=UTF8&z=18&ll=40.471196,-86.85231&spn=0.001873,0.003616&t=k&om=1)
Next, let's look at grades. My favorite site to do this is topozone.com.
When you look at the map, you can see that the grades north of the bridge (from 176 to 178) are not very steep at all (though they do get a bit steeper at, and just north of 178, going up as you go north). However, south of the bridge, there is indeed a grade, but I'm afraid it's not that steep. Let's see how we can calculate it. The Wabash river is at mile 176, and exit 172 is Route 26. Therefore, there are about 4 miles between Rt. 26 and the river. Over that time, you go from a 660 foot altitude (at mile 172) to a 540 foot alitude at the river. The average grade over those four miles is only 0.5% (downward going north). There are short sections where the grade is a few times more, but at most, it looks to be about 3%.
Good luck with this, and let me know if this information is helpful,