California Highways

California Highways

Numbering Conventions:
Signing in California/Signing Standards

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Introduction to
Signing in



Placement of Signs

[Sign Changing]In California, markers on highways were initially placed by the Automobile Associations (Automobile Club of Southern California and the California State Automobile Association). The California State Automobile Association (CSAA) was responsible for signing in the 45 counties of northern and central California starting in 1908 until 1969, and the Automobile Club of Southern California (ACSC) erected signs in the State's 13 southern counties from 1906 until 1956.

The first route markers appeared along California highways in January 1928. This was done at the expense of the membership of the clubs. The first road to be marked was US 40 from Berkeley to the Nevada state line. In Southern California, the first route to be marked as US 101 from Los Angeles to San Diego. Other routes marked in 1928 were US 48, US 50, US 66, US 80, US 91, US 99, and US 199. In 1934, the state began assigning sign route numbers to routes in the state, after which the auto clubs began signing state routes.

A short time after the auto clubs began installing signs, AASHTO published the Manual on Uniform Traffic Control Devices. This established standards in the marking and positioning of US Route markers.

In 1947, the California Department of Highways was assigned signing responsibility. At this time, all routes signed by the auto clubs were examined, and had their signage brought into conformance with the AASHTO standards. However, the CSAA continued to sign in cities and counties until 1969, and the ACSC continued until 1956.

Signing Standards

[Note: Much of the information on signing standards is derived from a posting on misc.transport.road by]

Many people ask why California's signing standards are seemingly so different than the rest of the nation. There is actually a reason, and it is not that California thinks its standards are better.

California has had the largest freeway system in the nation since the late 1940's; the first California freeway was the Arroyo Seco Parkway, which opened in 1940. By 1947, California had overtaken all of the eastern states in total mileage. Its freeway system was also one of the first to get seriously congested and to require provision of overhead signs. As a result of this aggressive construction program and early onset of congestion, the California Division of Highways (CDH) (now Caltrans) made a heavy investment in signs and sign hardware long before national freeway guide signing standards were developed and incorporated into the Manual for Signing and Marking of Interstate Highways (subsequently folded into the MUCTD).

The legacy of this has been twofold: Caltrans can set national standards to a large extent, but it also has a lot of overhead sign hardware at risk if the rest of the country decides to adopt a different standard and make it mandatory. In fact California was successful in getting most, but not all, of its freeway guide signing standards incorporated into the Interstate signing manual. The lowercase alphabet used for destination legends on freeway guide signs was developed by the CDH in the late 1940's, although initially it was paired with Series D at a taller letter height rather than Series E Modified (which is currently used for the uppercase letters in mixed-case sign text), and the sign backgrounds were black rather than green. Note that most of these black signs have disappeared, although a few remain (in particular, look for the black-background signs for the truck lanes on I-5 approaching Route 14 northbound). There were several white on black overhead signs on I-80 through the Auburn area up until about 1990, when the road was rebuilt and widened. However, most of the black signs were removed in the late 1970's—long after they had been superseded by FHWA standards specifying Series E Modified/lowercase.

A short list of national standards forced on Caltrans includes:

The most important reason for Caltrans' deviance from national standards in Districts 4 and 7 (San Francisco and Los Angeles respectively) is its reliance on porcelain enamel sign panels with reflective button letters. The green background is not engineer-grade or high-intensity retroreflective sheeting, as in other states, but is porcelain enamel baked onto steel (up to 1985) or aluminum. These signs were favored by Caltrans for many years because they last much longer than reflective sheeting signs—more than 40 years versus a maximum of 15 for most reflective sheeting signs—and the life-cycle costs were believed to be lower in spite of the much higher initial cost. This high initial cost was sunk before Caltrans realized the difficulties excess durability would cause in carrying out message revisions.

Porcelain-on-steel signs really can't be drilled without rusting, although Caltrans apparently does this often and this is a major cause of overlay plates ("greenout") falling or dangling off of signs. The freeways in Districts 4 and 7 are Caltrans' busiest and thus have had the largest number of message revisions. Guide signs on these roads therefore have been incorrectly dimensioned for their messages for decades. Caltrans addressed the rust problem by changing to porcelain-on-aluminum for signs not considered susceptible to crash damage (which were changed to reflective sheeting early on). It has now also abandoned its initial reluctance to use reflective sheeting, which is now much, much cheaper than button-copy both in initial and life-cycle cost, because its ubiquitous use in all other states allows sheeting manufacturers to capture scale economies.

However, it is so much cheaper to recycle overhead sign structures that have been taken for salvage that Caltrans project engineers are strongly encouraged—when not forced—to do this, even if a sign bearing the required legend must fail to comply with the design rules in order to fit on the recycled structure. As a result of its large early investment in freeways, Caltrans' maintenance yards have mountains of salvaged sign bridges, butterfly trusses, etc. The problem builds up as Caltrans is forced to go through environmental inquiries in order to build new storage yards. (Two are pending in District 7; there may also be one pending in District 4.) There is now a great deal of 'in situ' (in place) recycling, as in a pending US 101 project in Ventura County, where a new chord will be added to an existing truss in order to allow new signs to be installed, while incorrectly designed signs will be fitted onto many existing structures that currently hold signs correctly dimensioned for their original legend.

Some projects also have addenda tacked to them saying that sign structures originally marked as "REMOVE AND SALVAGE" are now marked "REMOVE" (presumably for scrap).

Note that the specification for every traffic sign is now online at note that with publication of the new California MUTCD Supplement, Caltrans has decided to redevelop the sign specification sheets as a supplement to the federal 'Standard Highway Signs'. This means that all specifications that duplicate sign designs (about half of the total) are being removed, pulling the total number of sign specifications from 1006 to about 550. Originally, Caltrans attempted to put each sign specification sheet online as a vector drawing embedded in an Acrobat file. This was substantial work, and so Caltrans has decided to scan old specifications to Acrobat and upload them. All of the HOV. lane signs and most of the guide sign specs that resemble standard sign designs used nationally have been redrawn and are available as vectors, but some unusual, California-specific guide signs (generally for approaches to freeways) are currently available online only as scans of the 1971 originals. Caltrans is proposing to convert all of its specs to the same format as the drawings in 'Standard Highway Signs'. This means eliminating all of the "policy" verbiage which is often attached to specs and covers usage rather than design. It also means doing away with the collar for each drawing, which encloses the sign drawing within a rectangular frame and has agency name, signature of Signs & Delineation chief, etc., and has been used ever since the modern series of sign specification sheets began in 1956. The sign drawing in each spec will also be in full color, similar to the modern 'S.H.S.' Caltrans had previously experimented with full-color drawings in the initial series of sign specs in 1996 (now long since withdrawn from the website) but soon abandoned it in favor of the traditional monochrome. At the moment only a few specs redrawn in 2004 are available in the new format. Caltrans is also conducting training sessions on the new sign approach; a PowerPoint presentation, given jointly on August 16 by the Caltrans engineer responsible for the Supplement and by a California F.H.W.A. representative, explains the major changes and is available at In brief, Caltrans' supplement perpetuates certain practices which do not conform to 'M.U.T.C.D.' standards (much less guidelines) but instead of demanding total conformity in accord with published deadlines, F.H.W.A. is reaching for "low-hanging fruit." This means, e.g., that yellow lines for crosswalks are safe for the time being, but Caltrans has to continue with the exit numbering initiative.

How are shields put on signs? On the newer signs which use microprismatic sheeting, the shields are generally formed by cutting the border out of white retroreflective sheeting and affixing it directly to the sign background, around the route number, which is also direct-applied to the background. The result is very clean in appearance and ages evenly. It is a huge improvement over the former practice (on ground-mounted small guide signs) of affixing an engineer-grade retroreflective shield to a non-retroreflective opaque green background. An example of the old way of doing things (reflective shields against O.C.B.) can be seen here; an even more unsightly example of the color contrast which develops as the sign ages is here. The new way is here. [This paragraph based on information posted by Jonathan Winkler on Usenet.]

Sign Layout

For many years, Caltrans has had its own 'Traffic Manual', because the California Vehicle Code requires all California road agencies to use a traffic manual approved by the California Traffic Control Devices Committee (CTCDC). The CTCDC has historically believed that California has so many unique signing situations that it would be excessively cumbersome to address these using either the FHWA manual directly or a state supplement thereto.

This calculus has changed recently, largely because the CTCDC has realized it can't prevent local agencies from using the FHWA manual, even when to do so violates the CVC, and using the federal manual allows the federal authority-to-experiment procedure to replace the state one in a greater number of cases. This saves state resources and gives the experimenting agency full legal cover (not just in California, but also at the federal level).

In addition, Caltrans has finally given in on retroreflective background sheeting on guide signs and also exit numbers, so it is simpler to adopt the FHWA manual (with supplement), rather than identify and eliminate differences between the MUCTD and the 'Traffic Manual', which might be considered substantial for purposes of disqualifying California from receiving federal highway money. A supplement is now being prepared, but is not yet ready.

In addition to the 'Traffic Manual', the basis for sign descriptions in project plans is the Caltrans Sign Specifications. Caltrans does not include shop drawings (pattern-accurate or otherwise) for guide signs in its plans, unlike Texas and many other states. Rather, sketches of the signs showing the legends (place names and route numbers, e.g.) and their Sign Specification numbers, but not their precise layout, are included in the signing plans for a given project. This is because the contractor responsible for a road project does not furnish the permanent signing, as in many (most?) other states. Rather, Caltrans contracts with a single sign supplier for the service of providing signs (of a certain type, e.g. porcelain-on-aluminum or retroreflective sheeting) for multiple road projects throughout all of California. Once the project plans are in hand, Office Engineer then passes on the signing plans to the signing contractor, who derives the layout details for each specific sign from the Sign Specification corresponding to that sign's code.

In principle the overall dimensions of the sign as specified in the project plans are identical to the outside dimensions given by the Specification for that sign. In practice, this often does not happen. Once he has the layout details, the sign contractor then uses them to fabricate the sign, which is then delivered to the Caltrans district managing the project, where the contractor for the road project—who is actually responsible for installing the sign—picks it up. Since there is no well-developed federal numbering system for guide signs and the MUTCD leaves sign design as free-form as possible (most of the nitty-gritty is downloaded to 'Standard Highway Signs' (SHS), and few states follow SHS in its entirety), this means Caltrans has to have literally over a hundred drawings showing various legend configurations for G-series (guide) signs.

However, overhead guide signs—particularly in District 4 and 7—tend to be 'sui generis' designs for two main reasons: (1) Message loading tends to be heavy; and (2) the pressure to recycle existing structures is greatest, because these two districts have the highest proportion of overhead signs. These two factors mean that an engineer designing a sign for an existing structure is unlikely to fit it into the existing space using the layout rules mandated in the Specification for that sign. There are two ways out of this quandary. One is to take the nearest sign code, add "SPECIAL" to it, and then indicate on the plans how the standard layout for that sign code is to be modified—typically by using letters of a given height, spacing arrows a given amount, etc. This is often done with pull-through signs, many of which are 'sui generis' in southern California.

Another way out, often used for signs which are too small for the required message, is to specify the correct sign code anyway and count on the sign contractor to chop the marginal spaces down (by equal amounts on opposite margins) so that the sign fits on the structure, even though it is ugly and does not comply with the Specification.

The main result of this process for procuring signs is to separate the sign and sign engineer much more than in other states. A Caltrans engineer can add a sign to a set of project plans without even "road-testing" the sign by generating a draft shop drawing in 'GuidSIGN' or 'SignCAD', and this often leads to defective plans and bad signing.

Introduction to Highway Numbering
Numbering: Eisenhower Interstate Numbered Routes

©1996-2004 Daniel P. Faigin.
Maintained by: Daniel P. Faigin <>.