Plans for the yet-to-be-approved Bel Air Costco show a 24-pump gas station alongside the 152,000-square-foot discount club store at the corner of Plumtree and Emmorton roads. But Costco’s traffic planners did not account for additional traffic that the fuel pumps are likely to generate — far more than just a regular store without fuel, Maryland State Highway Administration officials say.

Projected customer visits outlined in the project’s traffic study were based on the Institute of Transportation Engineers Generation Manual’s general classification of “discount clubs,” which combines estimates for stores with and without fuel pumps. State officials said due to the popularity of Costco fuel, the number of customer visits to the Bel Air Costco would be “significantly different” than locations without fuel pumps, and therefore the study does not accurately reflect future traffic volume.

The SHA advised the development’s traffic planner, Traffic Concepts Inc., to confirm the validity of their projected trip generation numbers with traffic data for existing, similar Costco locations and to make appropriate adjustments.

Traffic Concepts Inc., says it is abiding by Harford County’s traffic planning requirements, and declined the SHA’s suggestion.

Lawrence Green, a third-party traffic engineer who analyzed the Costco traffic study in May, warned that Traffic Concepts has underestimated the number of customer visits to the site by more than 1.3 million trips per year, and thousands per day.

Based on the discount club classification, Traffic Concepts proposed 13 traffic improvements to the surrounding roadways, including widening Plumtree Road, adding stop lights and turn lanes to Emmorton Road and surrounding intersections.

Per county code, intersections are rated on an A-F scale; all intersections are required to operate at least a D level of service. The traffic study noted that the intersection will operate at a D level of service.

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Residents near the proposed Costco said traffic flow in the area is already poor, and they worry about traffic and the dangers of entering and exiting their neighborhoods once the new store is built.

As of this week, Harford County has only approved the Bel Air Costco’s first conservation plan. Several other steps must be completed before the county grants final approval.

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