Weekday traffic at the Downtown and Midtown tunnels has dropped nearly 22 percent after tolls were instituted on the two crossings beginning Feb. 1.

The drop in weekend traffic was even sharper — about 28.6 percent, according to a news release from Elizabeth River Crossings, the private partner developing the project.

“The level of diversion experienced remains in line with ERC’s initial expectations,” the release stated.

While average weekday volume at the Downtown Tunnel was about 95,000 vehicles, the average last week was 69,319. On weekdays at the Midtown Tunnel, the average was 40,000 vehicles before the start of tolling but was only 34,224 on Feb. 8-9.

Assuming all the vehicles were passenger vehicles and traveled during off-peak hours, drivers have forked over $482,738.25 in the first week of tolling. The actual cost is much higher, since the rate is higher during peak hours and for vehicles with three or more axles.

Drivers without an E-ZPass transponder also are paying more. About 63.4 percent of the weekday trips and 57.7 percent of the weekend trips through the tunnels were made by vehicles carrying the device.

Motorists who elect to be billed by their license plate pay processing fees up to three times the toll rate.

In Suffolk, E-ZPass on-the-go kits can be purchased at the treasurer’s offices, 441 Market St. and 2000 Bennetts Creek Park Road, and at the Visitor Center, 524 N. Main St. An on-the-go kit includes the transponder and costs $35. Of the cost, $15 is available immediately for tolls, and the other $20 becomes available once the pass is registered.