Along Interstate 40 (I-40), business routes are found in the five westernmost states through which I-40 passes, California, Arizona, New Mexico, Texas, and Oklahoma.
The 4.24-mile (6.82 km) loop begins at I-40 exit 121 on the west end of town and proceeds northward, passing over the former SR 66, a local road still signed as a state route that is a former alignment of US 66.
The loop continues to the east side of Flagstaff, where Route 66 diverges carrying the former alignment of SR 40B (5), before intersecting US 89.
After crossing over the BNSF railway, the spur continues for 0.19 miles (0.31 km), ending just north of the intersection of Cooperstown Road and the county line.
It continues west after that, intersecting NM 41 before reaching its eastern terminus at a flyover interchange with an additional east-to-west ramp at exit 197.
The highway runs south from the interchange toward former US 66, then turns west along that decommissioned route where it terminates at the Texas–New Mexico state line.
I-40-B begins and ends at on- and offramps leading to and from two-way frontage roads along I-40, which, in the case of the one on the northbound side, is a genuine former section of US 66.
East of there at the intersection with Grand Avenue, the post office is diagonally across from a campground, and, beyond that point, the road runs past some silos.
I-40-C begins and ends at on- and offramps leading to and from two-way frontage roads along I-40, which, in the case of the one on the northbound side, is a genuine former section of US 66.
I-40-C passes a TxDOT construction and maintenance facility and then curves southeast again east of 3rd Street to follow along the southside of the former Choctaw Route.
The highway starts turning northeast at Tascosa Road/Gem Lake Road before running straight east at the North Western Street interchange.
I-40-D becomes a divided highway after an interchange with Loop 335 (Lakeside Drive) and runs along the northern border of Rick Husband Amarillo International Airport.
I-40-F begins at the offramp for exit 110, leading to the I-40 frontage road along the eastbound lanes, which suddenly becomes a divided highway named "Route 66".
The route runs along the edge of town as a four-lane undivided highway with the southside lined with numerous massive grain silos along the abandoned Chicago, Rock Island and Gulf Railway line until the intersection with FM 2300 (Eastern Avenue), and, after passing by a TxDOT maintenance facility, the road become a divided highway once again.
This oneway pair runs through the McLean Commercial Historic District and comes to an end just at the intersection with a connecting road that brings eastbound Bus.
I-40-J begins at the offramp for exit 161 leading to the I-40 frontage road along the eastbound lanes, which, just as in Groom, suddenly becomes a divided highway named "Route 66".
I-40-J then runs over the overpass above I-40 to turn right at the frontage road along the westbound lanes leading to the western beginning of the business loop.
I-40-J narrows down to a two-lane undivided highway before passing by a TxDOT construction and maintenance facility and then leaves the frontage road at the onramp to eastbound I-40, where it meets its terminus.
Between Maple and Poplar avenues, I-40 Bus./US-283/former US-66 has a grade crossing with a former Rock Island Railroad line, just west of a historic depot.
Just after James Way, the divided highway is replaced by a four-lane undivided boulevard with center left turn provisions, and the road approaches the National Route 66 Museum.
Between BK 35 and Country Club Drive, the road not only turns to the east again, but also resumes its previous status as a divided highway.
[39] Immediately after the intersection with South Glenn Smith Street, the road runs along the bridge over the Washita River, and the name is reverted to Gary Boulevard, where it becomes more rural.
curves to the northeast then turns right where it ends at another flyunder interchange, while historic US-66 continues onto East Main Street along the north side of I-40.
After passing by the Federal Correctional Institution of El Reno, the divided road narrows as it enters more developed surroundings.
Immediately after the westbound off- and onramps for I-40, the business routes all turn from north to east onto Hornbeam Road.
The only indication of that street's current importance are signs directing motorists to the Henryetta Municipal Airport and an RV Park.
turns south along this overlap until finally terminating at a cloverleaf interchange with I-40, which is also the northern terminus of the Indian Nation Turnpike.
The road is a commercial strip that runs at a slight north-northwest angle and serves as a four-lane undivided highway with occasional provisions for left-turn lanes.
East of North Dogwood Street, I-40 Bus./US-64 curves to the southeast, away from the former MoPac line, and resumes as a standard contemporary commercial strip.
ends at a partial cloverleaf interchange with I-40 known as exit 311, while US-64 continues toward the Sallisaw Sports Complex, Muldrow, and Moffett, where it crosses the J. Fred Patton Garrison Avenue Bridge over the Arkansas River and the Oklahoma–Arkansas state line.