Road-Related Information for New Mexico

Numbering of New Mexico Highways. New Mexico has had numbered routes since the 1920s. Originally, the numbering system was a simple and sequential bottom-up method, with principal through routes carrying the lowest numbers. In 1927, the new U.S. highway system was introduced, at which time state route numbers on the newly designated U.S. routes were eliminated (and freed for reuse on other roads). Between establishment of the U.S. route system and expansion of the highway network in New Mexico, there were significant changes in the numbering system from the late 1920s into the early 1930s. The route lists accessible from the home page will for now list only post-1927 routes. However, when a route has an original 1920s number, I will make note of it.

There are still vestiges of the original mid-1920s system, and a few routes still bear their original numbers from that era. The original system had routes generally numbered under 100, but as the state system grew, the number assignments were extended higher. By the 1950s, the state began to take responsibility for shorter, local roads. Numbers higher than 500 were assigned by 1960 (though it is unlikely that there were ever that many roads actually in the system at any one time), and today they go over 600. There is no longer any correlation between the significance of a route and whether it has a high or low number. While for the most part the current numbering system can only be described as "random" within the range of assigned numbers, there has been since 1988 a district-based numbering scheme that results in clustering of newly-assigned route numbers. More on this topic below.

There is no duplication of numbers between state and U.S. or Interstate routes. Back in the 1930s, state route numbers were changed if they duplicated a newly designated U.S. route. However, this was not done from the 1950s to about 1970, and during that time there were state highways numbered 10, 25 and 40 (the Interstates) as well as 56 and 82 (the newer U.S. routes) until about 1970. Even today, there is a NM-412, but U.S. 412, which does not exist in New Mexico independently, is not the official "inventory" number of U.S. 56-412.

In 1988, the state undertook a significant renumbering of the state route system. The "problem" this effort attempted to cure was that some routes followed complicated paths, connected with overlay sections on other state or U.S. routes. The solution was to establish a "no overlay" rule for state routes; any jog along another route, regardless of length, requires a new route to be established. This unfortunately broke up some routes that, though they had short overlays with other routes, were logical to maintain as continuous routes. Particularly hard hit were NM-44 (now restored as a continuous route as U.S. 550), NM-3 north of Las Vegas (519 and 522), NM-14 (337 and 55), and the state's longest route, NM-18 (209, 206, 402 and 406). The new routes established in 1988, when they were not designated as extensions of other state routes, were often numbered with three-digit numbers where the first digit is the NMDOT district number. This also explains why routes with numbers over 600 were established in western New Mexico (District 6), even though there are quite a few unused numbers under 600.

County Roads. New Mexico counties generally have marked routes, though there is no statewide designation system and no real attempt to coordinate numbering of roads that cross county lines. Counties use numeric, alphanumeric or alphabetical designation systems at their own discretion. Where routes are marked, the MUTCD (Manual of Uniform Traffic Control Devices) standard blue pentagon is generally used. While numbered county roads are often marked from state highways, they are only rarely marked on Interstate highway exit signs. The example at right is from San Juan County, which has probably the most systematically numbered county route system; the first two digits are geographic references within the county.

Speed Limits. The only statutory speed limits in New Mexico are 30 mph in business and residential zones, and 75 mph on other highways. The state may establish lower or higher limits based on design speed or a speed study. The following table lists typical speed limits for various classes of roads.

Highway construction standards. The only non-interstate highway freeway segments in the state are U.S. 70 for about 10 miles east of Las Cruces and a 13-mile segment of U.S. 84-285 north of Santa Fe. Otherwise, the only true freeways in New Mexico were the three Interstate highways that cross the state. There are no 3-digit interstates. Otherwise, New Mexico does have quite a few miles of four-lane divided highway along its major routes (U.S. 285 from I-40 south to Carlsbad, U.S. 550 from Aztec to Bernalillo, U.S. 70 from Las Cruces to Alamogordo, and many other shorter segments). Some of these roads are actually four lanes with a double-double line median. Future projects will expand U.S. 64-87 from Raton to Clayton and U.S. 491 from Gallup to Shiprock. By comparison, in 1926 the only paved highways in the state were from Albuquerque halfway to Santa Fe and from Las Cruces to the Texas border.

Relief routes. New Mexico has several roads with this unique designation --- unique because I haven't seen it used elsewhere in the country. As fancy as it sounds, a Relief Route is simply an urban bypass. They exist (at least that I've seen) at Santa Fe (NM-599, between I-25 south of the city and U.S. 84-285 northwest of the city); Alamogordo (officially U.S. 54-70 running west of the city); Carlsbad (NM-200), between U.S. 285 northwest of the city and U.S. 62-180 east of the city; and Roswell (still marked Truck U.S. 70-285 as of 2007, but all official information indicates that it is the U.S. 70-285 mainline, running west of the city).

Frontage roads. Many miles of interstate are paralleled by state-maintained frontage roads (often the old U.S. highway that predated the interstate). In a few instances, these roads are part of a state route and posted with a standard marker, but most often they are not marked at all. In places, there are frontage roads on both sides of the interstate. The sign at right is a very rare entity (though all state-maintained frontage roads have a similar number assigned for inventory purposes). This was taken along the east frontage road of I-25, south of University Avenue (NM-101) in Las Cruces. This road is not only numbered, but is also in the adopt-a-highway program. There are other frontage roads marked in southern New Mexico, and the signage varies slightly on some roads.

Indian routes. There are routes posted across reservation land that are referred to as "Indian" routes. Often, these are major connecting routes, but sometimes they are local roads that are not improved to any extent. I'm not clear on what entity is responsible for maintaining these routes, whether the Bureau of Indian Affairs or the individual tribe (I doubt the latter is the case). The route I took this photo on looked as if it were actually maintained by NMDOT, probably under contract to the funding authority.

Route markings. State roads were marked at least by 1927. Before that, route numbers were assigned, but I have not seen anything that would indicate if an official marker was used, "pole markings" (painted markings on telephone poles) were utilized, neither, or both. New Mexico has always used the zia --- the Indian sun symbol that is found on the state flag --- as the main element in its route markers. There have been, as far as I can tell, only two major designs of route markers (both depicted below). The first was a stamped circular yellow metal sign with the number inside the red zia and the legend STATE ROAD circling the top part of the zia. By about 1950, the design was modified to change the background color to white and add the letters N.M. on the bottom. I have no way of telling when this symbol went out of production, but probably no later than 1960. I lived in New Mexico from 1971 to 1977, and only saw one of these signs during that time, so there was time for an essentially complete changeover by the early 1970s. I am told that a transition design was used for a short time, similar to the MUTCD "default" state route marker (white circle on black square) but with "STATE" and "NM" curved across the top and bottom. I never saw such a sign and haven't attempted to use it in my route listings as an indicator of when a route went out of existence.

The current sign design has been used, with only minor variations, since some time in the 1960s (it was in almost exclusive use when I moved there in 1971). It has the number inside a red zia on a circular white background, surrounded by a black square. Occasionally, you see a sign without the zia, looking much like an Iowa route marker. A few of these when used for 3-digit routes are elliptical. The red paint used for the zia tends to fade, so some signs look like they were made without the zia when in fact they are weathered. Guide signs always use a plain circle (no zia) for state route markers, and newer interstate guide signs use an ellipse for 3-digit routes. Older interstate guide signs use circles for 3-digit routes.

U.S. routes are generally not marked where they overlay an interstate.

	This is a current and very typical NM route marker, essentially what was common when I moved to the state in 1971 (except signs were made of wood then). As you will observe as you tour my route listing pages, where I have photos of a number of individual route markers, the width of the zia and the height of the numbers vary greatly. Another problem with these signs is that red tends to fade faster in the intense New Mexico sunlight than other colors, and often a sign looks like an Iowa-style circle on square when in fact it originally looked like this. There are a few markers around that are circle-on-square or ellipse on rectangle, but they are generally at freeway interchanges and thus may have been manufactured by contractors.
	This style of route marker, a modification of the original yellow marker, probably was used during the 1950s. I believe I saw one like this on NM-100 in the early 1970s (I remember the "N.M" across the bottom). This sign was restored by Mike Wade of Artesia, NM, who kindly offered the photo for my use here. The lettering and zia were embossed, but the number was not - at least in the later years of these signs being used, the number was imprinted on a reflective background and applied in the center. It is therefore not possible to know what route this was originally posted on.
	I took Mike's photo (above) and modified it to show the design of the original (1927 until possibly the 1950s) route marker. These have long-since disappeared, but I found two different sources that describe this design. It's reasonable to assume the same features were embossed as in the sign above.

Return to New Mexico Highways Home Page

Updated March 20, 2008