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Interstate 19 shield
Interstate 19
Main route of the Interstate Highway System
Maintained by ADOT
Length: 63.60 mi[1] (102.35 km)
South end: Mexico Federal Highway 15.svg MX 15 at Mexican border at Nogales, AZ
North end: I-10 in Tucson, AZ
State routes in Arizona
< I-17 I-40 >
Unconstructed - Former

Interstate 19 (I-19) is an intrastate Interstate Highway located entirely within the state of Arizona. I-19 runs from Nogales, at the Mexican border to Tucson, at Interstate 10.[2]


Route description

In Nogales, Arizona, the southern terminus of I-19 is adjacent to the international port of entry, and southbound travelers can continue into Nogales, Sonora, Mexico, and connect with the northern terminus of Mexico Federal Highway 15. I-19 initially heads west through Nogales before making the turn to head north. It interchanges with two other state highways near the southern end of the route, SR 189 at exit 4 and SR 289 at exit 12. As I-19 enters the Tucson city limits, it has an interchange at SR 86 at exit 99 before reaching its northern terminus at a junction with I-10.


Nearly the entire route of I-19 follows, or is adjacent to, the former routing of U.S. Route 89 and the Santa Cruz River, which flows northward from Mexico, through Tucson and eventually disperses into the desert between Tucson and Phoenix. Most of the time, much of the river is dry, but heavy storms can cause it to overflow its banks.

The official "completion" date of the I-19 segment between Tucson (km 100) and Green Valley, Arizona (actually Helmet Peak Road at km 75) was February 12, 1972. A 1978 Project Report for the Arizona Department of Transportation lists entire I-19 project as "completed," which includes segments between Green Valley and Nogales, Arizona.

Metric-unit advance guide sign on Interstate 19, installed as part of the Valencia Road interchange renovation

Interstate 19 is unique among US Interstates, because signed distances are given in meters (hundreds or thousands as distance-to-exit indications) or kilometers (as distance-to-destination indications), and not miles. However, the speed limit signs give speeds in miles-per-hour. According to the Arizona Department of Transportation (ADOT), metric signs were originally placed because of the "metric system push" in the United States at the time of the original construction of the highway.

Interstate 19 had originally been signed as it was constructed, in a series of small signing contracts which used customary units.[3] In 1980, Arizona DOT awarded a single contract to install new signs which used metric units, to overlay English-unit expressions on some existing signs with metric-unit expressions, to install kilometerposts, and to provide bilingual signing in select locations. The signing scheme used in 1980 provided explicit units on advance guide signs, but not on interchange sequence signs or post-interchange confirmation (distance) signs. The expressions on advance guide signs were of the form "2 km" for distances over 1 km and "500 m" for distances under 1 km, with no provision for fractional kilometrages. On advance guide signs, the metric unit expressions "km" and "m" were placed on the baseline where "MILES" would otherwise have gone, but were sized so that their lowercase loop height matched the uppercase letter height of "MILES" on customary-unit signs. The exception was a handful of advance guide signs for the SR 86 Ajo Way exit, which used "KM" (in uppercase, contrary to SI nomenclature) on the same baseline and at the same letter height as "MILES." The 1980 signing plans also provided design details for speed limit and advisory speed signs using metric units, with the limit values enclosed in a red circle on the speed limit sign and a black circle on the yellow-background advisory signs. These speed signs all had explicit units, with "km/h" below the circle enclosing the limit value. However, the advisory signs were cancelled by change order and not installed. Had the metric speed limit sign been installed, the signed speed limit on I-19 would have been 88 km/h, which is a close soft-conversion of the then-existing 55 MPH "double nickel" national maximum speed limit. Information signs, to three distinct designs, were also placed at various locations on or near I-19 to advise motorists that the highway was signed in metric. Notwithstanding the metric legends, the signing plans were dimensioned entirely in feet and inches.[4]

In 1999, Arizona DOT awarded two contracts (administered as a single construction project) to renew the signs along the full length of I-19. The general approach toward metric signing differed from that taken in 1980. Explicit units were given not just on advance guide signs, but also on interchange sequence signs, post-interchange confirmation signs, and community interchange signs (the last-listed had not been used in 1980). On the distance signs, "km" appeared after each kilometer measurement except when one or more of the distances was a fractional kilomer. In such cases all the distances were given in meters with "meters" (written out in full, not "m") after each distance value. On distance signs in general, "km" or "meters" appeared on the same baseline and with the same letter height as the distance values, while advance guide signs were formatted as in 1980. Since a typical Arizona DOT freeway guide sign rehabilitation contract also replaces surface road signing near those roads' interchanges with the freeway, metric-unit signs also appeared on local roads near I-19, giving distances in kilometers to tourist attractions such as Mission San Xavier del Bac. As was the case in 1980, the signing plans were dimensioned in feet and inches.[5] However, a number of signs near the Valencia Road interchange were replaced or amended when it was converted from a partial cloverleaf to a SPUI in 2000. One of these signs has a fractional kilometrage greater than 1 km, rendered as "1500 m," while others use "m" rather than "meters" as the unit expression. Metric unit expressions on the advance guide signs installed or modified as part of this contract appear on the same baseline as the metric values, rather than on a raised baseline as on other I-19 advance guide signs. Again, the plans were dimensioned in feet and inches.[6]

Citing motorist confusion arising from the metric signs on I-19, Arizona DOT's Tucson district announced that new signs on I-19 would use United States customary units. To avoid the cost of replacing the metric signs all at once, signs would be replaced in specific areas of the freeway during construction projects in those areas.[7] New signs were put into place between Exit 99 (Ajo Way) and Exit 101 (Interstate 10) in 2004 after the completion of the new Interstate 10–Interstate 19 interchange.

A recent reconstruction project at the Interstate's northern terminus with Interstate 10 in Tucson, Arizona (at the interchange commonly called "The Crossing") was begun in 2002 and completed in August 2004.[8]

Exit list

County Location Kilometer (Mile)[1] # Destinations[9] Notes
Santa Cruz Nogales 0.00 (0.00) Mexico – United States border
1.90 (1.18) 1 Western Avenue (Target Range Road)
4.76 (2.96) 4 SR 189 Mariposa Road
8.55 (5.31) 8 I-19 Bus. south Grand Avenue (Business 19 not explicitly signed) Southbound exit only
12.42 (7.72) 12 SR 289 Ruby Road
17.53 (10.89) 17 Rio Rico Drive, Yavapai Drive
22.45 (13.95) 22 Peck Canyon Road
25.17 (15.64) 25 Palo Parado Road
29.34 (18.23) 29 Carmen, Tumacacori (Santa Gertrudis Lane) – Tumacacori National Historical Park
34.94 (21.73) 34 Aliso Spring Road
40.10 (25.92) 40 Chavez Siding Road
42.84 (26.62) 42 Agua Linda Road
48.39 (30.07) 48 Arivaca Road
Pima 56.26 (34.96) 56 Canoa Road
Green Valley 63.63 (39.54) 63 Continental Road
65.74 (40.85) 65 Esperanza Boulevard
69.72 (43.32) 69 I-19 Bus. north / Duval Mine Road (Business 19 not explicitly signed)
Sahuarita 75.48 (46.90) 75 Helmet Peak Road, Sahuarita Road
San Xavier Indian Reservation 80.32 (49.91) 80 Pima Mine Road
87.98 (54.67) 87 Papago Road
92.04 (57.19) 92 San Xavier Road
Tucson 95.10 (59.09) 95 Valencia Road – Tucson International Airport
98.35 (61.11) 98 Irvington Road
99.97 (62.12) 99 SR 86 Ajo Way
102.?? (63.15) 101 I-10Phoenix, El Paso
102.?? (63.28) 102 29th Street-22nd Street, Silverlake Road, Starr Pass Boulevard Northbound exit & southbound entrance

See also

Business routes


  1. ^ a b Arizona Department of Transportation. "2007 ADOT Highway Log". Retrieved 2010-01-13.  
  2. ^ Google, Inc. Google Maps – overview map of I-19 [map]. Cartography by Tele Atlas. Retrieved on 2008-02-15.
  3. ^ One example of such a contract was Arizona federal-aid project I-19-1(65), covering I-19 between its Nogales terminus and the Otero TI (title sheet signed August 7, 1970).
  4. ^ Construction plans for Arizona federal-aid project I-19-1(81) (title sheet signed January 17, 1980).
  5. ^ Construction plans for Arizona federal-aid projects NH-19-1(110) (Arizona DOT TRACS H260701C) and NH-19-1(116) (TRACS H260702C) (most sheets sealed March 1997).
  6. ^ Construction plans for Arizona federal-aid project ACNH-19-1(127) (TRACS H260901C) (most sheets sealed June 1999).
  7. ^
  8. ^ [1]
  9. ^ Substantially as shown in most recent sign rehabilitation plans; destinations not actually shown on signs in parentheses

External links

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