After 20 years of planning, the final leg of the Route 222 bypass project will begin this month in western Lehigh County, promising traffic adventures but an eventual end to the legendary congestion in that section of the county.

Motorists who have suffered through years of chronic traffic jams on Route 222 between Interstate 78 and Route 100 probably won't be subjected to much more torment, since much of the construction over the next two years will be done to the north — on the new parallel road that will become the bypass.

However, people who regularly travel the back roads in that section of the county will face traffic restrictions and detours. Engineers will try to minimize the disruption by keeping the old roads open until the new ones are done, said state Department of Transportation engineer Donald E. Lerch.

Tie-ups also are likely at the Kressler Road intersection with existing Route 222, near the Charcoal Drive-In and Bieber Bus terminal, where traffic from nearby Interstate 78 flows heavily. Direct access to the bus terminal and restaurant will be eliminated, and customers destined for the popular businesses will use a service road to be constructed to the south.

The 3.5-mile stretch of bypass being built in the final phase represents the longest leg of the new road. Work on a 2.7-mile loop west of Route 100, which will bend south, cross existing Route 222 and reconnect with Route 100 near Creamery Road, has been under way for a year.

When completed by July 2006, the four-lane, $140 million divided highway in Upper Macungie and Lower Macungie townships is expected to relieve the rush-hour congestion on existing Route 222, and to paint the lines of economic development and job growth onto western Lehigh County.

Six traffic lights will punctuate the 55-mph highway, helping provide access for area residents, as well as offer business opportunities to the fast-growing region.

In the final phase:

New bridges will be built over the Eastern Industries Inc. industrial property, Cetronia Road, and a section of Norfolk Southern rail line near Ruppsville Road. A bridge also will be built over the Pennsylvania Turnpike, requiring the toll road to be temporarily closed for up to three four-hour periods during off-peak times to install oversize girders.

In a series of traffic restrictions and detours that will change as the project advances, several roads will be relocated, included Krocks, Cedarbrook and Grange roads and Reppert Lane.

Mill Creek and Kressler roads will be extended, and Brookside Road north of existing Route 222 will be widened to provide access off the bypass.

Ruppsville Road and Reppert Lane will end in cul-de-sacs on both sides of the bypass, as will Krocks Road on the south side.

Seven intersections — including three on existing Route 222, also known as Hamilton Boulevard — will be enhanced or constructed anew.

PennDOT officials are expected to issue a ''notice to proceed'' on the final leg of the work after a meeting Tuesday with the general contractor, Balfour Beatty Construction Inc. The Canonsburg, Washington County, company was the low bidder for the $57.7 million contract.

With more than two years of construction still ahead, will the improvements be worth the temporary inconvenience for motorists, business owners and those who live near the work-zones?

Most residents and business owners are focused on the day the bypass will open.

''Hallelujah,'' said homeowner Herbert Bieber, standing in front of his property at 849 N. Krocks Road, just north of Hamilton Boulevard. ''It'll be a godsend.''

Krocks Road will end in a cul-de-sac instead of continuing north, so Bieber expects that much of the speeding traffic in front of his house will be reduced.

Bieber's neighbor, Ed Zettlemoyer, has replaced eight mailboxes in the 51/2 years he's lived on Krocks Road, as hasty motorists failed to maneuver a nearby curve.