Odd median-outer clearance situation on I-95 in Georgia

[Tom958]

Yesterday I drove I-95 from the GA-FL line to GA 204 near Savannah GA 57-99 for the first time in decades, and I noticed something very odd...

Starting during the heyday of Interstate highway construction in the early '60's, the standard median width for rural freeways in Georgia has been 64 feet. In the mid '80's, Georgia started widening many of these highways by adding two lanes and full-width shoulders in the median, leaving 16-20 feet of grass and invariably sporting a double-faced W beam barrier. The outer shoulders were left untouched. Now I suppose that over half of I-75 in Georgia is like that, along with sections of other highways including the recently-widened Forsyth County section of GA 400.

I-95 throughout almost its entire length in Georgia is six lanes with a narrow grassed median and a double-faced W beam barrier, and I assumed that it was the same as so much of I-75... until yesterday, when I saw this and two other original-equipment bridges with narrow right shoulders, surely only four or five feet wide! They're on the oldest section of 95, between GA 251 (the original bridge has been replaced there) and GA 57-99, including the latter. Sure enough, the remaining median on I-75 and most of the other similar highways is 40 feet, but on I-95-- all of it-- it's more like 50-52 feet. It's just not as noticeable along most of 95 because freeway bridges were built with larger outer separations starting in the late '60's.

So... it's obvious that the GA 251-GA 57-99 stretch of I-95 was built with a 64-foot median and bridge spans just long enough to accommodate ten-foot outer shoulders, same as at countless locations across the state. I'm guessing, too, that for whatever reason, it was decided that the medians on subsequent sections of I-95 should be 74 or maybe 76 feet, though those on similar highways built at the same time remained at 64 feet. Wassup with that? Then, when the time came to widen this nine-mile section of 95, it was decided to maintain the newer, wider median and accept the narrower shoulders under the bridges. But wait, there's more: Shoulders are generally less heavily constructed than traffic lanes, so in order to secure that extra 10-12 feet of median width, it would've been necessary to remove and reconstruct the shoulders instead of leaving them untouched as was typically done throughout the state.

The obvious explanation is that GDOT wanted the extra median width so that four lanes could be added in the median and there'd still be room for full-width left shoulders. However, that doesn't take into account the strangest feature of I-95 in Georgia: all of the major bridges over watercourse were built with an extra lane on the right side, and the section between miles 34 and 49 already has the fourth lane in each direction, though it's used only as auxiliary lanes between interchanges, being closed off by striping passing through interchanges. It also raises the question of why the same wasn't done across the whole state.

I'm at a loss to understand any of this. 

[froggie]

They could be taking a cue from the NYS Thruway and built the extra width in so as to allow 6 lanes (3 each direction) on one side during future bridge or pavement work.  The bridges over Fancy Bluff Creek and GA 303 (really all of the bridges between US 17 at Exit 29 and US 341, as well as bridges north of Exit 67) have this feature but the pavement width is not consistent on the segments between the bridges...it's normal 6-lane pavement width in between.

As for the segment between US 341 and GA 99, my hunch is that either GDOT did not do the proper environmental and traffic study paperwork to keep the 4th lane through the interchanges, or FHWA didn't sign off on allowing it.  Not that it really needs that 4th lane anyway through there.

[RobbieL2415]

Funny, because at the US 17 Interchange the shoulders underneath that bridge are practically double-wide!

Skimming along it does look like they built the bridges and underpasses with an expansion in mind but haven't felt the need to use it yet. They did this with I-84 (E) in Southington and Waterbury, CT when they modernized and added a climbing lane to an underpowered portion of the freeway.  It was stubbed at its western end in case a future project widened the highway to 6 lanes to downtown Waterbury (which is nearing completion now).

[Beltway]

However, that doesn't take into account the strangest feature of I-95 in Georgia: all of the major bridges over watercourse were built with an extra lane on the right side, and the section between miles 34 and 49 already has the fourth lane in each direction, though it's used only as auxiliary lanes between interchanges, being closed off by striping passing through interchanges. It also raises the question of why the same wasn't done across the whole state.

Stealth 8-lane widening.  Given the major environmental impacts with all those wetlands, streams and rivers along I-95, I figure that they wanted to do one widening of the original highway and not have to go thru the whole NEPA EIS process again, to do the construction once and not have to do it again in those sensitive areas.  Bridges widened to 8 lanes or replaced with 8-lane bridge (or twin bridges, etc.).  Roadway embankments widened to 8-lane cross-section.  Two 12-foot lanes added each way, with right lane currently used as shoulder (I would have to look at the design plans to verify this but the right shoulder is 12 feet wide thruout and I strongly suspect that my analysis is correct).  10-foot left shoulder built.

In the future when they want 8 lanes they will need to build a 12-foot right shoulder first.  The overall roadway embankment prism is wide enough to allow this.