Connecting Communities: How Smart Corridor Planning Gets People Going

Some streets just don’t get you where you want to go. At least not directly.

Streets organically formed from pre-automobile footpaths or commercial routes confuse travelers in Boston, New Orleans, San Antonio, Philadelphia, and other cities across the nation and around the world.

These days, experts in corridor planning carefully consider where, when, how, and why people will be moving between places. The process, which can take over five years from start to shovel-readiness, generally runs through these steps:

Feasibility study, or preliminary engineering report. “This is an initial concept, a look at different alignment alternatives with a high-level cost estimate,” says Justin Clark, P.E., PTOE, Managing Vice President, Transportation. This stage considers how people travel (autos, bikes, walking) and why (transit, freight, emergency services), and it identifies major constraints, such as right of way or utilities.

Along with line-on-a-map options for the corridor, there is also a high-level environmental analysis, which can uncover details that alter the plan, says Grant. “For example, the environmental constraints analysis for San Antonio’s South Texas Parkway found old oil wells all over the place, so we had to shift our alignment a bit to avoid them.” New corridors should steer clear of cemeteries, cultural sites, and flood-prone areas, too.

Detailed corridor analysis. “This is when we develop different viable alternatives for the corridor, including perhaps adding bike lanes, sidewalks, or a dedicated transit lane,” Justin says. “Then we weed out the bad options and perform more-granular analysis on the ones that will solve operational, safety, or other issues.”

The team consults the local Metropolitan Planning Organization(MPO), which has developed their own regional travel demand model based on census data, historical traffic data, mode split, and estimated future population and employment metrics. Their models consider separate Traffic Analysis Zones (TAZs) and predict the trips between one TAZ and another. They forecast the daily work commutes, school drop-offs, shopping runs, and other drives a future roadway will need to accommodate, collecting these origin-destination pairs into a giant matrix of data that informs the baseline corridor design.

“We give the MPO our projected volumes, alignment with planned intersections or interchanges, number of lanes, and projected speed limit. The model then estimates the traffic through each assessed corridor, balancing it throughout the network to optimize travel time,” Justin explains. The MPO analysis is a starting point, rather than the settled solution, says Associate Vice President Grant Wuebben, P.E., PTOE. “They update their models every five years, and many times we may know about a relevant new development before they do.”

It’s a collegial discussion between Pape-Dawson transportation engineers and the MPO, continues Grant: “On the South Texas Parkway, the traffic projections we calculated on our own were a bit different than theirs due to a few differences in assumptions. We discussed the discrepancies and ended up on the same page.”

Detailed modeling. Engineers further develop the few remaining corridor options. “We’ll continue with comprehensive modeling, put drawings together, calculate more-detailed opinions of probable costs, and finalize the traffic projections to get to our final option,” says Justin.

Public engagement is threaded throughout the process, but it takes center stage here. As with most projects on this scale, interested parties have competing interests and include private citizens and advocacy groups, as well as DOTs, utility providers, developers, and county and city governments. It’s not uncommon for a corridor to run through multiple municipalities, which creates additional challenges and opportunities.

Schematic and environmental analysis. As candidate options winnow down, the selected alternative gets a drainage study, utility review, right-of-way impacts list, roadway cost estimate, and more-granular environmental analysis. “We’re really trying to fine-tune our design now,” says Justin. “We use an evaluation matrix to take all factors into account and get our best, final option.”

At this stage, a detailed schematic and environmental process add specifics to the basic plan. Engineers provide more information about intersections, auto and bike lanes, sidewalks, and medians. The public gets to understand the project better and comment on it, which can result in iterative design changes to align with community desires.

Specialists focus on minimizing the amount of land to be acquired. “We try to follow property lines where we can, and we’ll work with landowners for purchase or land-swap, if necessary,” says Grant. “As we get down to a final option, we meet with affected property owners individually,” Justin adds.

The result is a complete schematic: an approved picture that shows what the roads, bridges, sidewalks, and bike paths will look like, without the engineering detail needed to build it.

Detailed plans. Based on the approved final schematic, final design goes through standard 30-60-90% milestones, with client reviews at each step. In the end, a Plans, Specifications and Estimate (PS&E) document is approved, and the detailed sheets are ready for the contractor to construct the job.

Construction. Pape-Dawson often continues with the project to completion, working directly with the contractor, verifying material submittals, managing requests for information, and modifying plans, if necessary. “Sometimes we’re still involved even after the corridor is open. For instance, if we’re responsible for signal work, we’ll come later to check the signal timing and make sure things are operating the way we intend and make any tweaks as necessary,” adds Grant.

The results are corridors that serve the people who will walk, bike, and drive across them for decades to come.