I was able to drive on highway 90 from the West Pearl River in Louisiana to Pass Christian Mississippi. I know that isn't the whole thing, but here is what I saw:
From The River to where 90 junctions with Highway 607 in MS is a two lane road with some shoulder. There was a 5 mile or so section that was freshly paved that looked ridable, but at least at 5 pm on Friday afternoon there was a high amount of fast traffic including many 18 wheelers. The part that was not freshly paved looked very rough and in some cases the shoulder was non existent. These stretches were short, but would put you on the main road at that time.
After the 607 junction the road heads toward Waveland MS and becomes a 4 lane divided highway. The shoulder is fair but the traffic is fast and the road is not freshly paved. It is rough driving in car and the shoulder doesn't look very nice. There was a lot of tire debris, gravel and weeds. If I were to bike to work I would have to take this road and I don't want to risk it.
Once you get into Waveland, there is of course city traffic and stop lights to deal with. The shoulder continues but this is also the turn lane. I am sure however you could find a side street that would be much easier to get through.
After Waveland is Bay St. Louis and it is just like Waveland. Highway 90 then crosses the Bay of St. Louis on a 4 lane drawbridge. The bridge is flat, but traffic is high, fast, and the sidewalk on edge is very narrow. You probably couldn't ride aloaded bike through there but you may be able to walk it.
Once you get a cross the Bay you are in Pass Christian. The highway goes over a high viaduct type bridge and (There may be another route around the steep bridge but the shoulder is good there) then continues along the beach. There is a narrow walk way and sometimes boardwalk that I believe goes all the way through Biloxi if I am not mistaken, but the traffic only gets more congested as you go through the towns to Biloxi.
I did talk to some of the riders in the Gulf Coast Bicycle Club who recommended getting on MapQuest and finding a side street to take you through most of the MS Gulf Coast. Old Spanish Trail is a street someone mentioned that goes straigh through at least some of the cities. They said once you get to Gautier, 90 gets quite nice, but I see that is not far from where the Southern Tier connects anyway.
I don't want to be a spoil sport not yet having done any touring, but I wouldn't recommend that route if you can avoid it.
This message was edited by jlsccjan on 6-26-05 @ 7:41 PM