Lane width on major arterials

[I-39]

I'm curious to know people's thoughts on this.

Background: They are proposing to widen US 31 through Spring Hill/Thompson's Station in Tennessee to a five lane cross section in the coming years. This is massively overdue if you are familiar with the area. However, they are considering widening it to narrower then standard widths (10-11 ft) as opposed to the (Tennessee) standard 12 ft. This concerns me a bit. This is a major roadway and it is already fairly tight through the area. Unfortunately, Spring Hill allowed a ton of development to literally hug the road on the north side of town, thus, making widening a challenge to begin with. However, I'm concerned that anything less than the standard 12 ft lanes will defeat the purpose and be more susceptible to accidents as cars are closer together.

So my question is, on a major arterial like US 31 in this area, is it better to go with the standard 12 ft lane or is 10-11 ft ok? How are standards in other states?

For reference, here are the preliminary plans.

https://onedrive.live.com/?authkey=%21AEBjKRVKD%5Fplw8s&cid=FE8AE11B532E1573&id=FE8AE11B532E1573%216542&parId=root&o=OneUp

[froggie]

11ft is an acceptable lane width in several urban/urbanized areas.

Some studies have even found city lane widths of around 10.5ft to be the "optimum" from a crash perspective.