Grover claimed that the cost picture of these kinds of structures don't support an obvious, straightforward "pre-built is cheaper" rubric; he stressed that if a community's issues and concerns about the needs and uses of the bridge are understood up-front and the bridge structure is well-thought out, a custom structure can be significantly cheaper than off-the-shelf. Grover did note that the project team would look at both options.

Grover opened with an explication of why the design process matters for bridges such as this one, centering his argument on four key points: a bridge that the community is proud of and which is designed to draw bike/ped users encourages the structure's appropriate use and discourages abuse/crime; upfront public input that this phase is critical to the design and structure being successful; this bridge will be the most visible element of the 20+ mile length of the ATT; and it's a multi-million dollar project whether an off-the-shelf or custom design is used, so the City needs to get it right.

A slideshow ensued showing a wide range of successful and, arguably, unsuccessful bike/ped bridges around the country. Bridges like this one face a design challenge in trying to meet two often conflictual goals. That is, bike/ped bridges should be as transparent/open as possible to provide visibility and safety for users, and to avoid creating a "tunnel effect" that makes it unwelcoming and discourages use -- but at the same time, highway design principles require such bridges to be 'missile-proof' from the perspective of preventing miscreants from easily throwing objects, or themselves, off the bridge structure.

Grover directly addressed and criticized the Cary US 1/64 bridge, for instance, by noting that the design combines these two goals in an incoherent way. An off-the-shelf, open-truss, inviting structure is directly in conflict with a vertical-plane chainlink fence that makes the overall design confused and makes the bridge, in his view, less successful.

One of the most significant suggestions Grover made in the meeting (again, seeking public feedback) is the recommendation to move the location of the I-40 bike/ped bridge slightly east, closer to the Fayetteville Rd. highway overpass. Though initially the bridge was intended to cross I-40 at the point where the existing Southpoint trail segment passes to the west side of the mall, Grover argues for making the crossing further east, closer to the mall itself.

The consultant demonstrated the biggest advantage of such a change with a topographical cross-section, noting that at the suggested new crossing point, the ground on both sides of I-40 is both naturally elevated above the highway and, importantly, is at a roughly equivalent height on both north and south ends of the freeway. Installing the bridge here, if the recommendation is accepted, would significantly reduce or eliminate the need for "ramping," or meandering ramps that lead up to a bridge that is much higher or lower than the trail's grade (see picture at right). Besides adding cost to the project, ramps also make bike/ped bridges feel less accessible and user-friendly, discouraging use.

Grover also noted that this bridge and trail segment seems likely to draw a range of uses, from bike commuters to dog-walkers to joggers to families and youth trying to get to the mall. To that end, he asked the audience for feedback on whether mall access would be a significant part of this bridge; Grover thought it would, and suggested that a more easterly crossing could allow access to both the ATT and quick access to the Southpoint mall.

One other factor playing into the bridge and trail design? Usage, or more specifically, anticipated growth in usage. The project team pointed out that within a 2 mile radius of the bridge project, as many as 10,000 new homes may be built in the next few years; the trail creates an opportunity for familes to "leave their pockets of cul-de-sacs," as one resident put it, and connect to a linear park. Which also means significantly increased usage, and possibly bike/ped crowding on the bridge, something Grover wants the project to keep in mind.

A few project facts: Ed Venable from the City optimistically gave a timeframe that includes a design phase for the bridge through June 2008; a bidding phase to run July through December 2008; and construction running January 2009 through June 2010.

The stickler, as always, is money. $4.865 million will be available for the project through NCDOT as soon as an inter-agency agreement between the City and the state agency everyone loves to hate is completed. However, the City thinks as much as $1.5 million will be needed to complete the project. (It should be noted that that $6.3 million cost includes both the bridge and remaining Phase E trail segments; the guesstimate provided Tuesday night is that the cost allocation is 50/50 to each project, so we're not talking about a $6 million gilded crossing here.)

Venable notes that the City will look at outstanding bond money from other projects and to NCDOT itself as possible sources for the remainder of the funds; Durham is also looking through its transportation department at outside grant sources. A fallback is to re-approach through the city's CIP and bonds process to try to explicitly allocate more funds as needed.

No matter what, the project gets more expensive the longer it waits to be built -- with Bill Bussey from Triangle Rails-to-Trails claiming the cost of the project escalates $1,600 per day. Which makes getting the design right, and getting the darned project started, more important than ever before.

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I've updated this post with Dan's Google Map (thanks again!).  Also of note, the City of Durham has posted PDFs of project maps and the survey distributed during the meeting on their web site; if you have survey feedback, please fill out the PDF survey and FAX or email it to the City contact listed on the form.