Arizona State Route 303

Loop 303 currently begins at Van Buren Street,[4] south of I-10 in Goodyear and at I-10 becomes a six-lane freeway with a stack interchange.[5] South of Van Buren Street it continues as Cotton Lane but without a route number. It heads north under McDowell and Thomas Roads, then over an interchange with Indian School Road. The road heads through a farmland terrain and passes the Wildlife World Zoo near Northern Avenue. It over passes a BNSF Railway spur line near Olive Avenue.[6] At an interchange with Greenway Road, Route 303 enters a residential community and turns northeast. The route heads over a bridge above Grand Avenue (US 60) along with another BNSF railroad line.[6] The route turns eastward and was recently upgraded to a six-lane freeway.[7] It turns north near the Happy Valley Parkway interchange and then east again south of Lake Pleasant, passing through planned arterial interchanges. The freeway comes to an end at a temporary at-grade interchange (eventually to be a stack interchange) with I-17 near Skunk Creek. East of this interchange, Route 303 becomes Sonoran Desert Drive. The south end from US 60 to I-10 is frequently used to bypass Grand Avenue and quickly move from Grand Avenue to Bell Road.[8]

Old colored Arizona Loop 303 shield that has been phased out.

Loop 303 was originally a part of the 1985 Maricopa County Regional Transportation Plan that was funded by a sales tax approved by Maricopa County voters. The freeway, designed to service the Northwest Valley, was originally designated SR 517 in 1985; the Loop 303 designation was first assigned on December 18, 1987.[9] The freeway was scheduled to be completed sometime by 2005. However, funding shortfalls and increasing construction costs forced cutbacks in the plan, and in 1995 the freeway was dropped from the regional plans.

Maricopa County took charge of what was then called the Estrella Freeway project when it was dropped from the regional freeway plans, maintaining it as an interim 2-lane highway along the original corridor while keeping the state route designation. The county then made significant improvements to the roadway, extending it several miles north and east of US 60. While the highway was still largely a 2-lane rural road, the extension north of US 60 along with the southern terminus just north of Interstate 10 was upgraded to a 4-lane divided parkway, and the segment between US 60 and Bell Road in Surprise was partially upgraded to controlled-highway standards with overpasses and right-of-way for on-ramps.[10]

With the extension of the sales tax approved in 2004, the highway was once again added to the Regional Transportation Plan. As Maricopa County had completed much of the required study and preparation work, construction on the freeway proceeded with a planned completion date of the I-10 to I-17 segment by 2015. According to an agreement between the state legislature and the state department of transportation, STAN (Statewide Transportation Acceleration Needs) funds were used to build a partial interchange at Bell Road in summer 2010, several years before previously intended.[11] In mid-2011 the segment between Happy Valley Parkway and I-17 was completed as a four-lane highway with an interchange at Lone Mountain Parkway completed but initially closed to the public. Motorists still have to pass through signaled ramp junctions at the I-17 Black Canyon Freeway until a full stack interchange is built between that route and Loop 303.

Long-term plans call for the extension of Loop 303 south of the interchange with I-10 in Goodyear to the planned I-10 'Reliever Route' Freeway, SR 30, and continuing south through Goodyear to connect with the planned alignment of future Interstate 11. Loop 303 would run concurrent with I-11 for several miles, before splitting off southward towards its ultimate terminus at Interstate 8 west of Casa Grande. Construction of this extension is expected to begin in Fall 2020. If completed, Loop 303 will serve as a Phoenix Bypass Route for both Southwestern Route going from Los Angeles to Tucson and Northwestern Route going from Los Angeles to Flagstaff.

In response to a projected budget shortfall of $6.6 billion brought on by the recession, the Maricopa Association of Governments voted to suspend funding to numerous projects during a meeting on October 28, 2009. Some modifications to Route 303, such as a scaled-back design of its interchanges with I-10 and US Highway 60, were made to cope with the budget shortfall. Funding for the extension south of I-10 to the planned alignment of SR 30 was removed, effectively postponing the extension until after 2025.[12]

The entire route is in Maricopa County.

Location	mi [1][13]	km	Exit	Destinations	Notes[14]
Gila Bend			60	I-8 – Tucson, San Diego	Planned interchange
			70	Vekol Valley Road	Planned interchange
Mobile			77	SR 238 (Maricopa Road)	Planned interchange
			82	Riggs Road	Planned interchange
			83	Chandler Heights Road	Planned interchange
			85	Queen Creek Road	Planned interchange
Estrella			88	Cotton Lane	Planned interchange
			90	Estrella Parkway	Planned interchange
			91	Rainbow Valley Road	Planned interchange, Northbound exit, and Southbound entrance.
			92	Rainbow Valley Road	Planned interchange, Southbound exit, and northbound entrance.
			93	Ray Road	Planned interchange
			95	Elliot Road	Planned interchange
Goodyear			97	MC 85	Planned interchange
			99	SR 30 (Tres Rios Freeway)	Planned interchange
	1.10	1.77	100	Edwood Street / Cotton Lane	Planned interchange, Southbound exit and northbound entrance.
	2.10	3.38	102	Yuma Road / Lower Buckeye Road	Planned interchange, No northbound signage for Lower Buckeye Road.
	3.20	5.15	103	Van Buren Street / McDowell Road	Northbound exit and southbound entrance; temporary counterclockwise terminus
	3.80– 3.97	6.12– 6.39	104	I-10 – Phoenix, Los Angeles	Stack interchange; signed as exits 104A (east) and 104B (west); exit 124 on I-10
	5.19	8.35	105	Thomas Road / McDowell Road	Southbound exit and northbound entrance
	6.17	9.93	106	Indian School Road
Goodyear–Glendale line	7.19	11.57	107	Camelback Road
Glendale	8.19	13.18	108	Bethany Home Road
	9.20	14.81	109	Glendale Avenue
	10.18	16.38	110A	Northern Avenue	Northbound exit and southbound entrance
	10.68	17.19	110B	Northern Parkway east	Trumpet interchange; west end of Northern Pkwy.
			111	Olive Avenue	Planned Southbound exit and northern entrance
Glendale–Surprise line	12.18	19.60	112	Peoria Avenue
Surprise	13.18	21.21	113	Cactus Road
	14.18	22.82	114	Waddell Road
	15.18	24.43	115	Greenway Road
	16.18	26.04	116	Bell Road
	19.29	31.04	119	US 60 (Grand Avenue)	Parclo interchange
Sun City West	23.68	38.11	123	El Mirage Road
​	25.68	41.33	125	Happy Valley Parkway / Vistancia Boulevard	Happy Valley Pkwy. was routing of Temporary Loop 303 before parkway's maintenance was turned over to Maricopa County
Peoria	26.88	43.26	126	Jomax Parkway	Interchange currently under construction with completetion date of late 2021/early 2022
	27.98	45.03	127	Lone Mountain Parkway
	29.18	46.96	128	Westwing Parkway	Planned interchange
	30.68	49.37	130	Westland Drive	Planned Interchange
	31.78	51.14	131	Lake Pleasant Parkway
Phoenix	34.58	55.65	133	Pyramid Peak Parkway	Planned interchange
	36.78	59.19	135	Stetson Valley Parkway	Planned interchange
	37.68	60.64	136	43rd Avenue	Planned interchange
	38.68	62.25	137	35th Avenue	Planned Interchange with frontage roads
	39.25	63.17	138	I-17 – Flagstaff, Phoenix	Clockwise terminus; at-grade intersection with frontage roads (future stack interchange); exit 221 on I-17; continues east as Sonoran Desert Drive
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Incomplete access       Unopened

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• "AZ 303". arizonaroads.com.