Clinched Highway Mapping

Jeff Morrison · Joined: 03 Aug 2008 Posts: 620

I posted this in the old group, but these things are unchanged and I've now been through downtown for a field check.

-On US 52, a typo in the point "I-74(3)3" instead of "I-74(3)"

-52 joins I-75 going south from I-74 (image and field check):
http://interstate-guide.com/images051/i-074_et_03.jpg

I think the "I-74(20)" point, which is very near "I-75", should be eliminated because the "I-75" point is on a ramp to US 127. "I-74(20)" is merely where the SB-to-WB ramp meets the more mainline NB-to-WB. Make the "I-75" point the common point for the 74/75 interchange. For US 52, this point should be "I-75(4)". Then, on 52, add "I-75(3)" with that point's coordinates, which is where 52 exits. US 27/127 is close there and we need another point at the Hopple/Central intersection:
http://maps.google.com/?ll=39.139081,-84.532896&spn=0.007173,0.012295
On 52, it would be "US27/127_N" and on 27/127 it would be "US52_W".

-I'd add the point "McMilSt" on 27, 52, and 127 for the intersection right by I-75 exit 2B because it's right by an interchange (and to flesh out a curve):
http://maps.google.com/?ll=39.124351,-84.533422&spn=0.007175,0.012295

Finally, some excessive nitpicking: the US 42 intersection is oddly offset from the one-way pair of 27/52/127 there. I think the point should be moved slightly west.
http://maps.google.com/?ll=39.10632,-84.519882&spn=0.007176,0.012295
On 52, this is US27Cin; on 27 and 127, US42_E; on 42, US52.

dfilpus · Joined: 14 Jul 2008 Posts: 717 Location: Chapel Hill NC

Downtown Cincinnati is a mess. I'm going through a complete redo, including all of your comments, which I found as well. The redo is using the routing in the OHDOT Straight Line Diagrams. The current map is simply incorrect in the location of some routes, especially US 22.

Every one of the downtown US highways on surface streets (US 22, 27, 42, 52 and 127) has separate one way segments that are sometimes several blocks apart. The current mapping is an attempt to split the difference. This has made the map a mess. To properly map the highways, each directional route should be mapped separately. OHDOT labels two routes for each highway: the R route or mainline and the D route or directional route. The R route follows the northbound/eastbound path for the highway. The D route follows the opposite direction or is multiplexed with the R route.

My first idea was to map the R route as the mainline and create a spur for the D route. What gets messy is when the highways multiplex with each other. US 52 and US 27 multiplex with each other in opposite directions. Each highway's D route follows the other's R route. This causes the mainlines to separate and merge.

A more practical solution is to only map the R route through downtown. For the US 27/52 multiplex, use the US 27 R route. I have implemented this routing on my own web site's maps.
_________________
Dave Filpus
http://roadgeek.filpus.org/

admin · Posted: Fri Sep 12, 2008 11:51 am Post subject:

If it's impossible to use a single set of points for both directions of route (like a widely separated couplet), use your last idea: just use points along one direction.

If you add a spur or extra route (US42_N etc.) for the opposing direction, then these parts of the routes double in reported mileage and become exceptions to the idea of a highway segment being "clinched" if you've only traveled in one direction.

You could possibly put one route of a multiplex on one direction's routing and another route on the other, if you think that would accomplish much.

I had the same problem with the current configuration of US 220/US 322 in PA when PennDOT moved one direction onto a new freeway and left the other direction on the old roads. There are places where the two routings are over 0.5 mi apart. I just picked the routing that would need a few more points so the user would have the flexibility to try to end a segment within the split route if needed.