The 86-acre Cottonwood development proposed for Dixon Lane would add up to 1,345 vehicles during afternoon peak hours to roads near Marcus High School and the Watermere retirement community, according to a 400-page traffic impact analysis first reported by the North Texas Sun. Several of the figures below are drawn solely from that report and could not be independently verified for this story, since the North Texas Sun's site could not be accessed directly during fact-checking; nothing found elsewhere contradicts them.

The study, conducted by Kimley-Horn and Associates and paid for by the developer, grades surrounding intersections and recommends improvements if the project moves forward. Fast food restaurants and Costco would generate the bulk of new trips, with 1,133 cars during the morning peak and 1,345 in the afternoon once the site is fully built out by 2031.

One intersection design choice remains unresolved: what goes at Dixon Lane and Whyburn Drive?

Roundabout vs. signal

A traffic signal at that intersection would produce an overall level of service of "B." A two-lane roundabout would score an "A" across the board. The roundabout, however, would be 200 feet wide, larger than the existing roundabouts on Chinn Chapel Road, and would require right-of-way from nearby property owners including Lewisville ISD.

Mayor Pro Tem Adam Schiestel said he wants to tie the development's approval to a guarantee that a roundabout gets built there.

"I like the idea of it being a traffic calming measure because everybody who hits this roundabout has to slow down in order to navigate it, it kind of discourages trucks and insulates the residential, high school area from the commercial area," Schiestel said at the Aug. 20 work session.

Planning and Zoning commissioners Scott Langley and Michelle Jackson have also voiced support for the roundabout, citing improved traffic flow and lower maintenance costs. Randi Rivera, director of planning and entitlement with McAdams, the engineering firm working with Cottonwood Development Partners, told commissioners the roundabout would likely cost more to build because infrastructure would need to shift northwest. If moved onto the developer's land, it would avoid the need to purchase right-of-way from LISD but would cut into a planned restaurant and retail building at that corner.

Town Communications Director Melissa Demmitt confirmed a roundabout is feasible but said the cost of either option would be determined during final engineering.

What the roads look like by 2036

The study assigns letter grades based on projected traffic flow:

• FM 407 and FM 2499: Currently rated "F" during afternoon peak. TxDOT construction is underway; the grade is projected to improve to "E" by 2036.
• Dixon Lane and FM 2499: Currently a "C," expected to drop to "E" in both peak periods by 2036 without improvements. The study recommends a westbound turn lane and a dedicated eastbound right-turn lane. The right-turn lane would be the only improvement paid for by the town; the developer covers the rest.
• Westbound Dixon Lane (FM 2499 to Whyburn Drive): Capacity rating of .89 during afternoon peak by 2036, approaching but below the failing threshold of 1.0.

The developer has expressed a desire to upgrade the planned Whyburn Drive extension from a two-lane collector to a four-lane minor arterial, which would bring its capacity rating from .93 to .38 during afternoon peak hours.

What's in the development

Phase I, targeted for May 2028, includes Costco, restaurants, a gym and 222,000 square feet of warehouse space. Phase II, by 2031, adds shops, a bank and 30,000 more square feet of warehouse. The Cross Timbers Gazette reported the site plan shows 24 buildings and three detention ponds. The land is currently zoned Agriculture.

Costco told commissioners at the Aug. 10 work session that Flower Mound households hold more than 15,000 memberships, according to the Cross Timbers Gazette, with roughly $150 million a year currently spent at the company's Lewisville location.

What's next

The land is zoned Agriculture. The project must clear the Environmental Conservation Commission, then receive a Planning and Zoning recommendation, before reaching Town Council for a final vote this fall. No hearing date has been set.

P&Z Chairman Gregory Schultz said at the Aug. 10 session, "While there is a lot of great opportunity here that we are excited about, there is also some legitimate concern with traffic," according to the Cross Timbers Gazette, and said commissioners would continue weighing resident input.