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This is not the place for a DDI. The area around this interchange recently got zoned for 20 story buildings. This is the natural extension of the North Hills area. If we build the infrastructure for it, there will be a surprising number of pedestrians around this area in very short order.
I have the same opinion about Western Boulevard as well, and when I raised my concerns with the NCDOT engineer responsible for traffic projections on the I-440 project, he bristled with irritation at the suggestion of accommodating pedestrians over vehicles.
Diverging Diamonds belong at places like Airport Blvd & I-40, or NC42 & I-40, where simply "accommodating" pedestrians without making them a priority is enough.
I'm in agreement with orulz. With North Hills expanding over towards Wake Forest Road and with developments such as Midtown East popping up in that area, we need bike/ped friendly alternatives in that area. Not a 10 lane DDI with 15' lanes and a skimpy 5' sidewalk.
I agree with both above, except for one teensy thing - pedestrian bridges are a big ole waste, because people don't use them. They're great ideas, do provide safe crossing but unless there's a physical barrier preventing pedestrians from crossing at ground-level people just make a goat path and forego the stairs/elevator. There are a host of other issues with ped bridges, but I think this one is the most important.
I don't think pedestrian bridges or tunnels are the greatest option either.
Wake Forest Road's interchange is kind of "substandard" in that it is a tight diamond, and that coupled with the proximity of development and relatively high property values means that options are limited. Conventionally, the stoplights along Wake Forest between the eastbound and westbound ramps would be at least 800' apart, but the spacing at this interchange is half that. As a result, they've already gone to the well many times for the "conventional" approach of just adding more lanes, and the well has run dry. Any further "conventional" approaches would involve a larger footprint to widen the spacing or add cloverleaf ramps, which would mean high-dollar property takings (Melting Pot or Days Inn or something).
That's why we're on to this more "creative" solution now.
But "creative" traffic engineering can be a nightmare for a pedestrian. Walking through a DDI as a pedestrian really sucks. It's no better than walking through a cloverleaf interchange. So, my honest preference for now would be to just Do Nothing. Table it for now, and investigate other ways to improve the transportation network that can take some pressure off this interchange.
I wonder if extending Six Forks to Capital could help? It's a common sense connection that has been in the plans for decades but never seems to go anywhere, presumably because a bridge over Crabtree Creek would be expensive. But if you take the nearly $7 million budgeted for this interchange, that's a pretty big down payment, right?
I don't think pedestrian bridges or tunnels are the greatest option either.
Wake Forest Road's interchange is kind of "substandard" in that it is a tight diamond, and that coupled with the proximity of development and relatively high property values means that options are limited. Conventionally, the stoplights along Wake Forest between the eastbound and westbound ramps would be at least 800' apart, but the spacing at this interchange is half that. As a result, they've already gone to the well many times for the "conventional" approach of just adding more lanes, and the well has run dry. Any further "conventional" approaches would involve a larger footprint to widen the spacing or add cloverleaf ramps, which would mean high-dollar property takings (Melting Pot or Days Inn or something).
That's why we're on to this more "creative" solution now.
But "creative" traffic engineering can be a nightmare for a pedestrian. Walking through a DDI as a pedestrian really sucks. It's no better than walking through a cloverleaf interchange. So, my honest preference for now would be to just Do Nothing. Table it for now, and investigate other ways to improve the transportation network that can take some pressure off this interchange.
I wonder if extending Six Forks to Capital could help? It's a common sense connection that has been in the plans for decades but never seems to go anywhere, presumably because a bridge over Crabtree Creek would be expensive. But if you take the nearly $7 million budgeted for this interchange, that's a pretty big down payment, right?
For DDIs with the pedestrian crossing in the center of the bridge, I believe it's superior to most other interchanges. The pedestrian movements are under signal control, and are much shorter. Plus, traffic only comes in one direction at a time. The DDI also provides an opportunity to cross the arterial, which is not reasonable/feasible for other interchange types.
For this DDI however, the pedestrian crossing remains on the outside, and I concur that it's very similar to crossing a full cloverleaf. I did ask to ensure that the sight distance for the crossings is adequate, but I'm not thrilled by it.
I agree that the ideal solution would be two additional off-ramp loops, but that would wipe out more than the Days Inn and Melting Pot in those quadrants. (The parclo-B, as this is called, is typically the most efficient type of interchange.) A full cloverleaf would be a disaster, as the weaving that would result on both 440 and Wake Forest would be terrible from both a capacity/operations and a safety angle.
This is not the place for a DDI. The area around this interchange recently got zoned for 20 story buildings. This is the natural extension of the North Hills area. If we build the infrastructure for it, there will be a surprising number of pedestrians around this area in very short order.
I have the same opinion about Western Boulevard as well, and when I raised my concerns with the NCDOT engineer responsible for traffic projections on the I-440 project, he bristled with irritation at the suggestion of accommodating pedestrians over vehicles.
Diverging Diamonds belong at places like Airport Blvd & I-40, or NC42 & I-40, where simply "accommodating" pedestrians without making them a priority is enough.
Why can't pedestrians be accommodated by making them cross at the only 2 signals points (one at each end with a refuge island) of the diverging diamond?
Pedestrians cross to the side opposite of the left turners in which the the right turners have already exited just before the signal w/refuge island and then back to other side at other signal/island.
These DDI increase flow and save time by 30-40%. They're a good thing.
I agree that the ideal solution would be two additional off-ramp loops, but that would wipe out more than the Days Inn and Melting Pot in those quadrants. (The parclo-B, as this is called, is typically the most efficient type of interchange.) A full cloverleaf would be a disaster, as the weaving that would result on both 440 and Wake Forest would be terrible from both a capacity/operations and a safety angle.
How many additional properties/buildings are we talking about in terms of buildings for the parclo-B? (I guess I'd have to see it on picture, can't visualize it in my head too well!)
Why can't pedestrians be accommodated by making them cross at the only 2 signals points (one at each end with a refuge island) of the diverging diamond?
Pedestrians cross to the side opposite of the left turners in which the the right turners have already exited just before the signal w/refuge island and then back to other side at other signal/island.
These DDI increase flow and save time by 30-40%. They're a good thing.
The design of this DDI pushes the pedestrians to the outside (where they are now.). The current bridge has piers in the middle that make it impractical to put the pedestrian down the middle. There are a few DDIs with pedestrians on the outside, including the one on US 17 in Leland.
I’ve looked at DDIs that make traffic operations worse. They are NOT for all locations. That said, the analysis indicates that this is a reasonable location for one, given the limitations of space. DDIs make for a good retrofit. For new construction not as clear cut. Some yes, some definitely no. So, careful with the blanket 30-40% better statement.
Pierre, for the Parclo-b, put 250’ radius loops in the NW and SE quadrants. Don’t have Google Maps handy, but I know it would be pretty disruptive. Better yet, measure a loop at Six Forks and then overlay it at Wake Forest.
Would the proximity with the signals at Wake Towne and Navaho be a potential problem with the DDI? (with the hospital on one side and the Wegmens development adding traffic onto Wake Towne)
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