I-526 extension at odds with goal

Finishing the Mark Clark, Interstate 526, freeway extension is proving to be a disappointing way to deal with traffic and growth problems. Recently-made traffic projections for the year 2030 reveal that the Mark Clark extension fails in its major purpose - to relieve congestion on arterial routes.

On U.S. Highway 17, the reduction in year 2030 traffic (6,000 daily vehicles), resulting from completion of the Mark Clark offsets the 20-year growth in traffic on U.S. 17, but not enough to cure congestion. On Maybank Highway, the Mark Clark extension relieves congestion to the east, but only at the expense of a large increase in traffic to the west of the extension, as well as on the Maybank Highway's feeder, Bohicket Road. On Folly Road, the Mark Clark extension reduces future volumes by 5,000 daily trips (around one-half of a lane of capacity) but still leaves the road congested.

With its two bridges over the Stono River, the Mark Clark extension does add two new cross-island links: between Johns Island and the peninsula to the west, and between Johns Island and James Island to the east. However, the benefit of this added cross-island access is degraded by focusing all new access to and from Johns Island to a single "hot spot" at the proposed (and only) interchange on Johns Island.

The Mark Clark extension runs counter to the region's growth management goals. The 2006 assessment of community impact of the Mark Clark extension established that it would induce a large increase in population in areas intended, in local comprehensive plans, to remain rural or lightly populated.

That the Mark Clark extension is proving to be disappointing is no longer surprising to transportation planning professionals. Building freeways for urban traffic is an idea now going on 60 years old and is showing its age and ready for retirement.

The freeway's bunching of traffic onto a single spine, while limiting access to less than one point per mile is, we now know, the worst possible way of handling urban traffic with its short trip length and myriad of origins and destinations. By contrast, a well-connected system of at-grade arterial streets, supported by a web of smaller collector streets and even smaller (and often privately-built) local streets is now understood to be optimal for carrying urban traffic.

The defining feature of freeways - strictly limited access - is hopelessly at odds with what we now want cities to be. The land consumed for freeway interchanges, not an issue in rural settings, is a major problem in cities, and the interchange with its limitation of access "poisons" the adjacent land for urban development. The well engineered at-grade intersection, on the other hand, needs far less land per vehicle moved, while at the same time creates a focus for travel destinations, arranged into community centers.

A long-standing (but usually unspoken) motivation for many urban freeways - to make a vast area of suburban and rural land available for tract housing development - is out of date. Cities are no longer seeking to decant population. To the contrary, cities are now far more interested in keeping and attracting permanent residents in their revitalized neighborhoods and emerging loft districts, and in once again hosting the travel destinations (jobs and shopping) serving these residents.

An early goal of urban freeways - to foster long distance commuting between traditional downtowns and new suburbs - has also come and gone. This goal is particularly obsolete in Charleston, a city with long leadership in understanding that quality of place trumps the need to get in and out of the place quickly.

The era of seemingly limitless funding for roads has ended, as revenue (tied to cents-per-gallon fuel tax) grows sluggishly while maintenance costs skyrocket on the huge, aging mileage of roads built in the past four decades. Price tags of 40 to 60 million dollars per mile, routinely (and realistically) budgeted only a few years ago, now appear to be ludicrous. In a national trend toward "right sizing," several state DOTs, most notably Pennsylvania's, are revisiting big-ticket road projects, replacing them with smaller projects that capture most of the benefit of the original project, but at a relatively small fraction of the original cost.

Charleston is by no means alone in having the completion of an urban freeway challenged. At least two dozen U.S. cities are at some stage of withdrawing plans for (or actually eliminating segments of) urban freeways. Typically, motivation for these initiatives are dissatisfaction with freeways as an urban traffic solution combined with the emerging view of cities as self-contained, sustainable places better served by local access rather than high-speed mobility.

The long "yes/no" debate over the Mark Clark extension has diverted attention from the more up-to-date fixes for the problem. At the heart of these fixes is network - specifically, multiple, direct and accessible links rather than a single new link (freeway) of limited access. Network includes not only the major arterials and new river crossings, but also the supporting web of collector and local streets, in many cases obtainable through alert intervention in the land development process.

An important part of the fix is correcting the blighted form of development along arterial highways, through low-cost local code prerogatives. These measures improve transportation in two important ways: (1) by reducing drivers' distress with their travel experience, thereby improving their perceived traffic service and (2) reducing traffic flow friction through better access and parking practices.

In all fairness, in the not-too-distant past some things could be said for urban freeways, explaining their lingering popularity as a planning concept. With their large right-of-way footprint, they are unquestionably a bold idea, and therefore answer the need to "do something" about traffic. Their big-ticket price tags get a lot of improvement projects underway with relatively small administrative burden. The public involvement, if any, is simple and efficient. The messy and laborious collaboration with neighborhoods that is needed to plan at-grade network improvements is not needed.

There is a need for better local access and inter-island connection, and the Mark Clark extension controversy has, usefully, kept attention directed to this problem while also establishing a scope and budget for a fix. The current challenge is to look beyond the tired "yes/no" options for an obsolete idea, and bring forward fresh and appropriate ideas.

Walter Kulash, P.E., is a consulting traffic engineer who has worked on numerous Lowcountry projects for local governments and private builders and formerly was a member of the Orlando firm of Glatting Jackson Kercher Anglin.