Of all the fictional freeway ideas I've had, this one's probably the most realistic.
US route 23 in Delaware County is a joke. On paper, it looks like a perfectly fine segment of the main road between Columbus and Marion — and Findlay, Toledo, Detroit, and so on… There's even a freeway segment to get motorists conveniently through the core of Delaware. However, what's not so obvious on maps is that north and south of that freeway section, the road is a slow suburban arterial choked with local development and too much traffic. The speed limit is 45 MPH through much of the county. Generally speaking, the road was not built to carry high volumes of traffic at high speeds. It's extremely disappointing in the context of the rest of the Columbus – Toledo corridor, which is entirely freeway or expressway at 65 MPH north of the Delaware/Marion county line. This corridor carries as much traffic as many intercity Interstate highways, so it's not unreasonable to expect a continuous, at-least expressway-grade route.
It would appear that, decades ago, planners assumed that US 23 would be converted to freeway through Delaware County when the need arises in the far future. Unfortunately, that need arose more quickly than anticipated, and now such an upgrade would be expensive and disruptive beyond any measure of feasibility. The Mid-Ohio Regional Planning Commission's 2009 long-term transportation plan includes nearly a thousand projects for Delaware, Franklin, and Fairfield counties between now and the year 2030. It does not include large-scale upgrades to US 23. An addendum lists projects that were considered but dropped from the plan, including upgrading US 23 to freeway north of Delaware. While that would be nice, it would still leave the section from I-270 to US 42 a choked mess; MORPC apparently didn't deem it worth pursuing, anyway.
Back in the late 90's, Interstate 73 was big news in Central Ohio. The preferred routing would have followed I-270 around the east side of Columbus, then up I-71, west along US 36 a few miles, then north and northwest to meet US 23 at the base of Delaware Reservoir. US 23 north of that point would then be upgraded to a full freeway and become I-73.
Then for some reason it was decided that Ohio would not pursue I-73 or I-74. I think the biggest factor in that decision was a perception that existing roads in that corridor were already sufficient. Apparently the decision-makers weren't familiar with the weak link in Delaware County, which has only gotten worse since then.
A few years ago, I was frustrated with the low speed limits and traffic lights along US 23 in Delaware County. I knew the state had pretty much given up on it, but I was convinced that a practical solution could still exist. I looked at USGS topo maps, and noticed a couple of gaps in the Delaware Reservoir Wildlife Area. After a bit of work in my budget CAD software, I had found an alignment that was sensitive to local features, and made for a shorter trip than Ohio's official I-73 alignment. I also drafted interchange layouts at either end, as well as a vertical profile. It looked great in my head, but I didn't yet have the tools to make a pretty map.
In the intervening time I have become active with OpenStreetMap. Partly because of this, I have begun experimenting with Debian Linux. Most recently, I discovered the forums at aaroads.com where I intend to share my plan for Interstate 171.
This map was developed using many of the same tools used by OpenStreetMap and its contributors. I used a tool called JOSM to edit OSM data, adding in I-171 from my existing plans. You can download my I-171 map data, but please don't re-upload it to OpenStreetMap. Not only would that add an entirely fictitious Interstate to a map that purports to be accurate, but several minor features would be mangled due to some minor changes I made for the sake of presentation. Anyway, the process of deriving the map you see on the left from that data parallels very closely the way OpenStreetMap provides its main map presentation, with the primary differences being cosmetic — also, OSM represents the entire planet, while my map only covers a small region in Ohio.
Anyway, back to the subject of I-171. I imagine it as a four-lane freeway, though pragmatically it could be built first as an expressway and upgraded later. It's about 17 miles long, and would save at least 15 minutes on a trip from central Columbus to Marion and points north, versus taking US 23 through Delaware. The northbound destination is Marion, and the southbound destination is Columbus. An auxiliary guide sign on I-71 northbound would indicate I-171 can also be used to get to Toledo. I-71 would be widened to 3 lanes each way north of I-171 (actual widening planned) and 4 lanes each way between I-171 and SR 750. Actually, SB I-71 would be 5 lanes for some distance downstream from the I-171 merge, possibly as far as US 36, depending on a traffic forecast study.
In conjunction with the opening of a new interchange along I-71, perhaps at Big Walnut Road, Interstate 171 would open up eastern Delaware County to explosive development, perhaps necessitating further widening to both of those Interstates and a new east-west expressway corridor across the south edge of Delaware. And explosive development doesn't have to be a bad thing, as long as infrastructure improvements are made concurrently and a master plan is followed.
This idea is entirely my own. I stress this not to claim credit but to emphasize that it's not in any official plans and therefore not likely to happen. On the other hand, if someone with MORPC or ODOT's Transportation Review Advisory Council were to stumble upon this concept, I hope that someone can see its merits.