Calculated, of course, by dividing total interstate mileage by total number of interchanges.
My guess would be Vermont, anyone know where I might find the data to calculate this?
Are we counting full interchanges only or each exit (ex: 5A/B, 5C)?
I know that Illinois is no slouch in that department. There are numerous sections where one can travel more than 10 miles between freeway interchanges (why limit it to interstates only? a freeway is a freeway is a freeway!), even near Chicago.
Whatever I can find. I'd prefer to count each "interchange" separately - for example, exits 142A and 142B on I-90 here in Madison would be counted together as one interchange, since they both go to the Beltline, but exits 309A and 309B on I-94 in Milwaukee would be counted as two interchanges, since 309A goes to 35th Street and 309B goes to 26th - but I recognize that there are probably lots and lots of special cases that could make an exact determination of the number of interchanges difficult.
Sounds good. I'll see what I can make of Louisiana
Quote from: Brandon on March 07, 2014, 02:16:04 PM
I know that Illinois is no slouch in that department. There are numerous sections where one can travel more than 10 miles between freeway interchanges (why limit it to interstates only? a freeway is a freeway is a freeway!), even near Chicago.
It's already complicated enough to assess with just interstates (ex: I-180, I-587, Alaska). Do we really need to add a debate about whether the Taconic is or is not a freeway on top of it?
Quote from: HandsomeRob on March 07, 2014, 02:16:32 PM
Whatever I can find. I'd prefer to count each "interchange" separately - for example, exits 142A and 142B on I-90 here in Madison would be counted together as one interchange, since they both go to the Beltline, but exits 309A and 309B on I-94 in Milwaukee would be counted as two interchanges, since 309A goes to 35th Street and 309B goes to 26th - but I recognize that there are probably lots and lots of special cases that could make an exact determination of the number of interchanges difficult.
I can think of a zillion of the special cases just off the top of my head. I-495 (NY) alone is essentially one giant pot of spaghetti.
Vermont has 320.22 miles of Interstates (per https://www.fhwa.dot.gov/reports/routefinder/table3.cfm), and by my count 53 interchanges, for an average of 6.04 miles/interchange.
vdeane: I'm pretty sure it's not going to be New York - let's call it a hunch.
How about Maine? It's mostly I-95.
OK, I get, for interstates only, an average of 3.54 miles for Illinois. There is a total of 2,182.03 miles of interstate with approximately (by my count) 617 interstate interchanges.
This is heavily skewed by I-90, I-94, and I-290 in Chicago. Taking those three out ups it to 4.20 miles between interchanges.
Quote from: HandsomeRob on March 07, 2014, 02:23:22 PM
Vermont has 320.22 miles of Interstates (per https://www.fhwa.dot.gov/reports/routefinder/table3.cfm), and by my count 53 interchanges, for an average of 6.04 miles/interchange.
That's technically and accurately calculating it based on how it appears the question is phrased, but I have a feeling that the original poster is looking for something different, which I don't really know how to calculate.
It seems to me like I-81 in Virginia has an exit about every five miles or so.
Quote from: hbelkins on March 07, 2014, 03:37:54 PM
Quote from: HandsomeRob on March 07, 2014, 02:23:22 PM
Vermont has 320.22 miles of Interstates (per https://www.fhwa.dot.gov/reports/routefinder/table3.cfm), and by my count 53 interchanges, for an average of 6.04 miles/interchange.
That's technically and accurately calculating it based on how it appears the question is phrased, but I have a feeling that the original poster is looking for something different, which I don't really know how to calculate.
It seems to me like I-81 in Virginia has an exit about every five miles or so.
(I am the original poster)
I calculated 3.41 miles/interchange in Iowa. It kinda surprises me that this is a lower average than Illinois.
Ok for Louisiana there are 921.2 total miles of interstate, and I counted 359 exits. Give or take a few based on on our own opinions. That gives a ratio of 2.57 miles between each exit. I'm a little shocked to be honest. I pictured Louisiana's interstates a bit more rural. I'm sure I-110 and I-10 through New Orleans made that number lower.
I may attempt to be a glutton for punishment and try Texas....
Quote from: HandsomeRob on March 07, 2014, 02:23:22 PM
vdeane: I'm pretty sure it's not going to be New York - let's call it a hunch.
1. Those were just examples. I'm sure the broader situations they cover apply to almost every state.
2. Wouldn't it be nice to see a ranking in the end? To that end, we would want to standardize the measures so that we're not comparing apples to oranges.
3. The distance between exits in NYC on interstates is actually larger than one would think. On the LIE for example, the distances between exits can be measured in miles even in Queens. (though I still wouldn't expect NY to be able to compete with a state that had few urban freeways period)
Anyone want to figure out a good way to measure Alaska?
Quote from: vdeane on March 07, 2014, 05:22:43 PM
Anyone want to figure out a good way to measure Alaska?
There doesn't seem to be anything strange with it. They seem like normal interchanges.
Quote from: 1 on March 07, 2014, 05:49:51 PM
Quote from: vdeane on March 07, 2014, 05:22:43 PM
Anyone want to figure out a good way to measure Alaska?
There doesn't seem to be anything strange with it. They seem like normal interchanges.
Then you don't know what an Interstate in Alaska is.
Not that I thought this would be anywhere near the top of the list, but my reckoning puts California at 2457 miles of Interstates with 1744 exits=1.4 miles per exit.
FWIW, here is Nevada:
Interstate 80: 92 exits in 410.674 miles
Interstate 580: 19 exits in 30.09 miles
Interstate 15: 35 exits in 123.77 miles
Interstate 215 (only counting the portion between I-15 and I-515): 12 exits in 11.3 miles
Interstate 515: 18 exits in 20.54 miles
Total: 1 exit every 3.39 miles
Delaware scores an average of 2.25 miles between each exit with 40.61 total interstate miles and 18 (ish) exits. Needless to say, we don't win.
For Maine, it's almost exactly 4.
OK, here's the point I'm trying to make. I'll use I-24 in Kentucky as an example, since it has no partial exits. Also please note that I am not including the new Pennyrile Parkway exit in this determination.
There are 16 exits (not counting the new Pennyrile terminus, rest areas and weigh stations) on I-24. The first exit is Exit 3 and the last exit is Exit 89. Assuming that the distance between each exit is the exit number, the total distance between exits is 86 miles. 86 divided by 16 is 5.37.
However, the total length of I-24 in Kentucky is 93.373 miles. Divide that, and you get 5.84. There is a difference, although it is small. A long distance between the state line or the route's terminus and the first exit would skew that difference, such as the first exit on northbound I-75 is 11 miles inside the state.
I was thinking Texas might have few exits because of I-10 out west. However, I think I-35 and interstates east of it will bring the average down. Good luck counting them bassoon.
Quote from: 1 on March 07, 2014, 05:49:51 PM
Quote from: vdeane on March 07, 2014, 05:22:43 PM
Anyone want to figure out a good way to measure Alaska?
There doesn't seem to be anything strange with it. They seem like normal interchanges.
Alaska has about 1,081.5 miles of interstate. Most of these miles are two lane roads with at-grades and driveways.
Quote from: hbelkins on March 07, 2014, 09:40:35 PMHowever, the total length of I-24 in Kentucky is 93.373 miles. Divide that, and you get 5.84. There is a difference, although it is small. A long distance between the state line or the route's terminus and the first exit would skew that difference, such as the first exit on northbound I-75 is 11 miles inside the state.
But why would you not want to allow that 11 miles without an exit to "skew the difference"?
Quote from: hbelkins on March 07, 2014, 09:40:35 PM
OK, here's the point I'm trying to make. I'll use I-24 in Kentucky as an example, since it has no partial exits. Also please note that I am not including the new Pennyrile Parkway exit in this determination.
There are 16 exits (not counting the new Pennyrile terminus, rest areas and weigh stations) on I-24. The first exit is Exit 3 and the last exit is Exit 89. Assuming that the distance between each exit is the exit number, the total distance between exits is 86 miles. 86 divided by 16 is 5.37.
However, the total length of I-24 in Kentucky is 93.373 miles. Divide that, and you get 5.84. There is a difference, although it is small. A long distance between the state line or the route's terminus and the first exit would skew that difference, such as the first exit on northbound I-75 is 11 miles inside the state.
But you're actually attempting to measure the average length of segments between interchanges, of which there are 15, not 16. That count adjustment should approximately offset the mileage adjustment.
Either method (93/16 or 86/15) seems valid to me. The difference is whether you're including the last few miles on the ends.
Montana: average of about 5.0 miles between interchanges (239 interchanges, not double-counting interchanges between Interstates or on the I-15/I-90 duplex), about 1196.2 total Interstate mileage (not double-counting about eight miles on the I-15/I-90 duplex).
Utah: about 3.8 miles between interchanges. Utah has some stretches of I-70 and I-80 with very, very low interchange densities, but its average gets killed by the interchange-dense Ogden-Salt Lake City-Provo area.
There may be other candidates in the mountain states and upper Midwest. Montana seemed the most likely since it has no major metro areas to drive up the interchange count, and lots of sparsely-populated rural areas to drive down the interchange density. South Dakota, Idaho, and Wyoming would be worth checking out as well. (North Dakota has too many metro areas; Nebraska has lots of interchanges per mile in the Omaha and Lincoln areas, and similar for Kansas.)
I double-checked Vermont which was mentioned above (easy to check the interchange count -- just for this exercise, sequential exit numbering is better than mileage-based), and somewhat to my surprise it has Montana beat. Who'da thunk?
I think interchanges where two Interstates cross should indeed count double. A 3-way Interstate interchange (terminus of one route, or one end of a multiplex) should count as one-and-a-half. A five-leg interchange, assuming all five legs carry Interstates, would count as 2½.
Or, if we're really concerned with exits then freeway-freeway interchanges shouldn't count at all.
Quote from: vtk on March 08, 2014, 12:54:10 PM
I think interchanges where two Interstates cross should indeed count double. A 3-way Interstate interchange (terminus of one route, or one end of a multiplex) should count as one-and-a-half. A five-leg interchange, assuming all five legs carry Interstates, would count as 2½.
Or, if we're really concerned with exits then freeway-freeway interchanges shouldn't count at all.
For the states likely to have the lowest interchange densities, these aren't going to make much of a difference. Vermont has only three Interstate-to-Interstate interchanges out of 53; Montana has five out of about 240; and Utah has nine out of about 200.
Quote from: Kacie Jane on March 08, 2014, 05:23:13 AM
But why would you not want to allow that 11 miles without an exit to "skew the difference"?
Because that's not between exits within the state.
Ok. Here's my best attempt at what I found for Texas:
Total miles of Interstate: 3,532.39
Total number of interchanges: 2,074
1.703 miles between exits. Which is blown way out of proportion by I-35 and the huge metro areas in Texas...
My attempt at Oklahoma: 936 interstate miles / 354 interchanges = 2.64 mi/ic. This is somewhat lower than I was expecting. I expected the I-44 turnpikes to pull the average up, but the 3dis pulled it down considerably.
The UK has 2173 motorway miles and 667 interchanges (a rough count), giving us 3.26 mi/ic
Given the population density (661.9/sq mi) is more than all but 4 US states (NJ 1205, RI 1016, MA 852.1, CT 741.4. Fifth is MD at 606.2), the mid-western interchange density does point to a difference in design philosophy over here.
Quote from: english si on March 17, 2014, 02:59:37 PM
The UK has 2173 motorway miles and 667 interchanges (a rough count), giving us 3.26 mi/ic
Given the population density (661.9/sq mi) is more than all but 4 US states (NJ 1205, RI 1016, MA 852.1, CT 741.4. Fifth is MD at 606.2), the mid-western interchange density does point to a difference in design philosophy over here.
One of the main differences is urban freeway versus non-urban freeway. Urban freeways (such as I-94 and I-290 through Chicago) have a very dense interchange to mile ratio. In fact, some of them are flipped. The ratio for I-90/94 for a one mile segment between I-290 and Hubbard's Cave is 0.125 miles/interchange. From what I can see, urban freeways tend to be rare in a lot of other countries, including the UK. That alone may account for the difference in the ratio numbers. When I ran the numbers for Illinois, it was 3.54 miles/interchange for the state as a whole. When I took out the densest interstates (I-90. I-94, and I-290), the ratio jumped to 4.20 miles/interchange. How different the ratio might be if London had several urban motorways through the central city?
And Arkansas:
If you count the FHWA interstates (30,40,55,430,440,530,540,630) its 647.32 total miles, 242 interchanges, 2.67 miles an interchange.
If you include:
unsigned I-130 - 660.02 miles, 250 interchanges, ratio of 2.64
future I-49 (AR 549) - 686.32 miles, 256 interchanges, ratio of 2.68
future I-555 - 735.22 miles, 276 interchanges, ratio of 2.66
The rest of I-49 one day between Fort Smith and Texarkana would add some miles to this ratio for sure.
Quote from: Brandon on March 17, 2014, 03:10:16 PMHow different the ratio might be if London had several urban motorways through the central city?
Probably about the same, as if you managed to get the Ringways through, then you'd pick up a few more urban routes (Belfast, Glasgow and Tyneside particularly) that add a lot of junctions per mile, but would have also got rural motorways like the M67, Strensham-Solihull, M31, M64, M100, etc that would have had above average gaps.
London would have been about 1.5 miles between junctions, if not more. The M100 would add a similar distance, with about 6 miles between junctions. It cancels out...