Business routes of Interstate 5
Business routes of Interstate 5 exist in both California and Washington. There are no business routes in Oregon as that state does not assign such designations for any of its Interstate Highways. However, Oregon Route 99 essentially acts as a business route for most of Oregon, along with OR 99W and OR 99E, which also has its own business route in Salem.
California
Interstate business routes in California are assigned by the California Department of Transportation, but are not maintained by Caltrans unless they overlay other routes of the state highway system. Local authorities may request route assignment from the Caltrans Transportation System Information Program, and all requests require approval of the executive committee of the American Association of State Highway and Transportation Officials.Chula Vista business loop
Interstate 5 Business was a business route of I-5 in San Ysidro, Chula Vista, and National City. I-5 Bus. followed the original routing of US Route 101 along Beyer Boulevard, Broadway, Harbor Drive, and Pacific Highway. The route terminated at I-5 at both ends.The designation was assigned in the 1960s and removed in the 1990s.
San Diego business loop
Interstate 5 Business was a business route of I-5 in San Diego. I-5 Bus. followed the original routing of US 101 along Mission Bay Drive and terminated at I-5 at both ends. The designation was removed in late 2004 and early 2005.Solana Beach
San Clemente
Irvine business spur
Interstate 5 Business is a business route of I-5, starting at I-5 in Irvine and ending at Barranca Parkway in Irvine, traveling via Jamboree Road. The spur intersects with State Route 261 adjacent to the northern terminus of the spur.Glendale–San Fernando Valley business loop
Interstate 5 Business in Glendale, Burbank, and the San Fernando Valley was a business loop of I-5 that followed present-day San Fernando Road in the 1970s. Prior to the construction of I-5, San Fernando Road was an alignment of US 6 and US 99.Woodland business loop
Interstate 5 Business in Woodland begins at I-5 exit 537, runs west on Main Street, and then north on SR 16 to exit 541.;Major intersections
Arbuckle business loop
Interstate 5 Business in Arbuckle, at, begins at I-5 exit 566, an interchange with no northbound reentry. The route runs seamlessly north from the offramp to Fifth Street through downtown Arbuckle, then turns west onto Freeway Underpass Road to exit 567, while Fifth Street continues north as Frontage Road. Both interchanges are signed for "Frontage Road".;Major intersections
Williams–Maxwell business loop
Interstate 5 Business in Williams begins at I-5 exit 575, runs north on Husted Road, and then northwest onto Frontage Road and Old Highway 99W, which runs along the west side of a former Southern Pacific line, now part of Union Pacific Railroad. Within downtown Williams, the route takes a reverse curve away from the tracks into Seventh Street where it intersects SR 20 Bus. but then returns to its previous trajectory before running under a bridge for SR 20, which has one connecting road between the two routes on the northwest corner. North of Williams, the route passes through the unincorporated community of Cortena, where it shifts from northwest to north. Entering Maxwell the road makes another slight shift away from the former SP line, but not as far away as in downtown Williams. It intersects Oak Street and Maxwell-Colusa Road, and then shifts back to its previous trajectory at a mobile home park north of North Street. I-5 Bus. continues along the west side of the tracks until ending at a half diamond interchange with I-5 with only southbound offramp and northbound onramp at exit 588. Old Highway 99W simply continues northward as County Road 99W.;Major intersections
Willows–Orland business loop
Interstate 5 Business is one of the longer business loops at that runs between Willows and Orland, though most of the signage is as Historic Highway 99W. The route begins at exit 601 on CR 57 and turns east. The segment is merely from the northbound onramp before turning north onto Old Highway 99W, running along the west side of the same UP line mentioned in Williams and Maxwell. The route follows the historic U.S. Route past a bridge over a canal where it becomes South Tehama Street, and then North Tehama Street at the intersection with West and East Sycamore Avenues. At the intersection of West and East Wood Street is SR 162, he first major intersection with the business route and the only one in Willows outside of its southern terminus. North of SR 162, the North Tehama Street name fades away as route makes a slight northeast curve where it crosses a railroad spur leading to a Johns Manville insulation plant and then curves back north again running closer to that UP line.Leaving Willows, I-5 Bus. passes through farmland, interrupted briefly by communities like Bluegum, where it curves away from the tracks to run along Walker Creek, only to cross a bridge over that creek and resumes hugging the side of the tracks again. The next community is Artois, where it moves northwest further away from the old SP line than it was in Willows but still turns back north again. Continuing its journey through rural Glenn County, I-5 Bus. passes through Grapit, then crosses a bridge over another canal to enter Greenwood. The route begins moving closer through the tracks as it continues through rural land and returns to the tracks after CR 20. The road returns to more rural setting as it enters Orland where it becomes Sixth Street and edges away from the tracks for local buildings on the east side. The intersection of Newville Road and Walker Street is where I-5 Bus. encounters SR 32. Two blocks later, the road hugs the side of the tracks again, and the road runs under an arch at a short bridge over the Stony Creek Irrigation Canal immediately south of the intersection with Almond Way. The tracks curve to the northeast away from the route just before the bridge over Hambright Creek where the road enters Wyo and then runs over a longer bridge over Stony Creek. After passing CR 9 then CR 8 on the east side, the business route turns left onto CR 7, while the former US 99W continues northward as "Highway 99W". Approximately west of there, I-5 Bus. ends at exit 621 on I-5.
;Major intersections
Red Bluff business loop
Interstate 5 Business in Red Bluff, at, has historically been part of both US 99 as well as US 99 Bus. It begins on I-5 at exit 647. The route runs along South Main Street, on the west side of an old UP line until after the intersection with the driveway to Red Bluff Shopping Center where it curves to the northeast and crosses under a trestle for that line. The route maintains that northeastern trajectory until just before it crosses a bridge over Reeds Creek, where the name changes to Main Street.At Oak Street and Antelope Boulevard, I-5 Bus. is joined by an overlap with SR 36. Two blocks north of there, northbound I-5 Bus. and westbound SR 36 has an intersection with Walnut Street the road that leads to Shasta College. Less than three blocks later, the backyard of businesses along the east side is a bend in the Sacramento River, and I-5 Bus. and SR 36 curve to the northeast just north of that bend at Dog Island Park. The routes run parallel to the former SP line again, but this time on the west side before approaching the intersection with Adobe Road. The northern terminus of SR 36 ends where that route heads west toward Fortuna, just before the bridge over Dibble Creek. The last intersection with both directions of I-5 Bus. is with Hess Road just before the route approaches the flyover interchange with I-5 at exit 651, which contains a southbound offramp and northbound onramp. The last intersection for northbound I-5 Bus. is with Via Del Roble just before the aforementioned onramp with I-5.
;Major intersections
Cottonwood
Anderson–Redding
Dunsmuir business loop
Interstate 5 Business is a business route of I-5 in Dunsmuir. I-5 Bus. followed the original routing of US 99 along Dunsmuir Avenue at exits 729 and 732, but it also has an additional interchange at exit 730, where it switches over from the east side of I-5 to the west side.;Route description
I-5 Bus. begins at a trumpet interchange at Dunsmuir Avenue. The first sites along the road are a gas station and convenience store, two motels, and a self-storage facility. The route winds through the mountains of the southern outskirts of the city, passing by the Dunsmuir Lodge motel. Between the intersection with Katherine and Hill streets, it runs alongside the Dunsmuir Cemetery, officially entering the city limits halfway though. The route runs between Dunsmuir City Hall on the west side and Siskiyou County Sheriffs Office just before entering the Dunsmuir Historic Commercial District between Cedar and Spruce streets.
Exit 730 is a partial diamond interchange on the northbound side where the off- and onramps do not connect to one another, and a southbound right-in/right-out interchange with a wide gap between the two ramps divided by the Sacramento River as well as Tauhindauli Park. North of the southbound offramp with exit 730, I-5 Bus. moves closer to the southbound lanes of I-5 and runs beneath the south end of Siskiyou Avenue which contains a bridge over both Dunsmuir Avenue and I-5. Near a local road named Scarlet Way, the road moves away from the interstate with mostly residential wooded surroundings. Across from the Castle Rock Water Company, Dunsmuir Avenue becomes Mott Road with a parking lot for the Hedge Creek Falls Scenic Area, while I-5 Bus. makes a right turn onto the north end of Siskiyou Avenue, and ends at a diamond interchange with I-5 at exit 732.
;Major intersections