I think that whenever the I-85 connector is FINALLY completed, this needs to be seriously explored because there's no reason to have an aging freeway running through a fast-growing urban area when there's a brand new interstate a mile away. I am pretty sure that a 147 rebuild is on the horizon given its age, and Durham shouldn't settle for a new freeway like Winston-Salem did.
This would be my preferred alternative. Coming out of the interchange with the I-85 connector, 147 would instead follow the tracks more closely and merge onto Pettigrew St. It would follow Pettigrew up to Fayetteville St, where it would then transition onto Jackie Robinson Dr. At the ATC, 147 would transition back onto the current ROW. At the Chapel Hill St intersection, it would shift over just slightly onto William Vickers Ave before transitioning back onto the existing ROW. As 147 approaches the Duke East Campus, it would transition onto Erwin Rd briefly before reverting back to the current ROW once past the Anderson St intersection. From there, 147 would follow the existing ROW up to US 15/501 at which point it would transition back into a freeway before merging with I-85.
I'm not sure how realistically feasible any of this is, but I think that the section from the I-85 Connector to ATC wouldn't be that difficult, and would allow for construction of the urban boulevard to commence without disrupting very much traffic. Also, rerouting 147 onto Pettigrew/Jackie Robinson would allow for the complete removal of the existing route which would result in normal-sized blocks, instead of tons of roads all parallel to each other within the same block.
Edit - been playing around with this for wayyyyy too long. I decided that extending Morehead St from ATC to Alston Ave by connecting various exit ramps and side streets, then having Morehead follow the existing 147 ROW to the I-85 Connector would be a great way to have a second urban road parallel to Pettigrew. This would allow for the removal of the Freeway, but would avoid creating absolutely massive blocks south of Pettigrew/Jackie Robinson. Both Morehead and Pettigrew would run parallel from ATC to Briggs Ave, at which point both would revert to one-way streets and morph into a freeway. I think that Morehead could be the higher volume route, while Pettigrew/Jackie Robinson could be a lower volume street that is designed primarily for bicyclists and pedestrians. At the ATC, where 147 would rejoin the existing route and carry higher traffic volumes, while bicyclists and pedestrians would be routed along a different parallel road (maybe Main St).
Here is the link to my map on Google Maps if you want to look at it more closely. (You'll probably see other infrastructure ideas around the Triangle as well that I've toyed with). Not perfect but I think it addresses most of the issues that have been raised about building an urban boulevard.
It's great that you solved one problem that I brought up (parallel streets close together) and another problem that I didn't (construction disruption).
The next post in the series goes into some of the math, but I limited the length of the boulevard because I thought that the return wouldn't be able justify the construction costs further out from the core. That said, if there would be a need to rebuild the freeway anyway, perhaps some of those funds could be utilized for a longer boulevard, which could create nice, first ring, dense residential neighborhoods with their own, smaller commercial footprints.
Yeah, I wasn't sure where it should start or end, but ideally I think the less freeway between the I-85 Connector and I-85, the better. I remember about a mile long segment of Bus 40 (Peters Creek Pkwy to the Innovation District) in Winston-Salem was rebuilt a few years ago for just over $100M, which included the replacement of 8 bridges and the construction of 2 pedestrian bridges. I think $100M would go farther here in Durham because freeways are more expensive to rebuild than normal roads.
The continuous section between the I-85 Connector and US 15/501 (running along Pettigrew, Jackie Robinson, William Vickers, and Erwin) is 5.66 miles. The Morehead Ave section from ATC to Briggs 2.31 miles. There are a bunch of side streets and other miscellaneous street reconnections that are probably around 1.5 miles in total.
All of the green sections in my map add up to just over 100 acres. Granted, this figure is based off of tons of rough estimates of where ROW/existing property boundaries are, but should be fairly close to an official survey.
Tough to put a number on how much those 100 acres are worth because property values vary massively depending on where you are along 147. The ATC area looks like about $1.5M-$2M per acre (before improvements), but drop off pretty rapidly the farther away you go. However, if development starts to crop up along this corridor, you'll really start to see those values skyrocket - Van Alen has a taxable value of $77M, and about $70M of that is the building. 555 Mangum has a taxable value of just over $38M, and $32M of that is the building. Combined, that's over $100M worth of improvements in just one block. Definitely playing the long game with these numbers, but I think the increase in tax values would probably eventually cover the cost of the conversion.
Fair - and if the remaining trips are locally generated, then I am thinking that there should be a more local solution.
The traffic counts on 147 are a good example of induced demand. If 147 didn't exist, the downtown street grid (as imperfect as it is in Durham) would more than be able to absorb the trips due to the fact that a grid of many interconnected streets has a surprising amount of capacity.
A boulevard would be a much better solution for people living in the area. The only people that would be negatively impacted would be the "through traffic", which would now have the connector to 85 to switch to. Traffic counts would be absorbed by:
1. I-85 connector
2. Other routes in/around downtown
3. The boulevard itself. With 4 lanes, albeit slowed down, it will still have decent capacity as a major roadway.
Those numbers are fascinating though regarding the lower volumes as you get towards downtown and lower still as you get to I-85.
Seems to me that there isn't a lot of through traffic going all the way from I-85 to the Connector, and the bulk of traffic is either heading to RTP or just trying to go a few streets down 147. I think that by having multiple streets running parallel to each other, the congestion that does exist will be mitigated, and at least theoretically those short trips could be walked or biked more feasibly as long as the streets are designed correctly. But I'm just an armchair traffic engineer.