Width of Vehicles

The law specifying the maximum vehicle width for Arizona is below,  and for comparison, the UVC is also copied.

There are two limits, one more restrictive for any-old street, and another which allows wider trucks/buses but only on prescribed streets:

  • The general rule for any vehicle that may be driven on any street is “total outside width of a vehicle or the load on the vehicle shall not exceed eight feet” (96 inches). It says nothing special about mirrors. Just 8 feet period… but for whatever reason it’s just assumed mirrors “don’t count” toward the eight feet.
  • The next category is wider, but restricted to particular subset of roads (interstate and other types of listed highways, and/or designated by the local authority) of 8.5′ : “total width of the vehicle or the load on the vehicle of not more than one hundred two inches, exclusive of safety equipment“. I take it that mirrors are safety equipment, and thus can stick out without any limitation. (unlike, e.g. CA which allows no more than 10″ of mirror protrusion on each side)

This all, of course, has to do with lane sharing. Below is a depiction of what happens in a 12′ lane when a cyclist rides at the right edge, and the driver of a common medium-duty pickup (Ford F-250 shown) tries to squeeze by without changing lanes…

Too narrow to share...


Arizona has some extra-special rules that let RVs be wider than 8.5 in some cases. As this article points out, MANY RVs are 8.5′ wide, and this is in many cases/places not allowed because of the 8 vs. 8.5 thing… and goes on to say the rule is rarely enforced.

The UVC has relaxed rules about where moving companies’ 8.5′ trucks can operate.

Where are Super-sized trucks/buses allowed?

The stuff about state and/or federal aid highway system (#1, 2, and 3) is clear enough, as the entire state can be just looked up on that map. #5 is a bit of a catch-all which means that they are permitted on just about any arterial road; note that the word “highway” may not mean what you think it does (highway is simply synonymous with street).

The local authority truck routes is sortof confusing; I tried looking into the City of Phoenix — Code of Ordinances, Chap 36, Traffic is here.  At first I thought it was defined in Sec. 36-160 “Schedule III — Through truck routes”. There you will find a specific, and quite limited list of routes; there are only 10 in the entire city; e.g. “Buckeye Rd from 19th Ave to west City limits”. The online version includes a nearly-illegible map. Also, I note that that ordinance claims authority via   §28-1106, which doesn’t seem correct. That statute is some sort of temporary restrictions measure; it should probably refer to  §28-1093(4) instead.

Moving on, there is a pamphlet issued by the city of Phoenix, Digest of Truck Route Ordinances which has a (legible, and in color!) map, where I note that all arterials are colored green, which the legend says is “truck route”. This led me to what appears to be the likely best answer:

36-88.03 “Exceptions to route and traffic zone restrictions… A. Trucks may operate any time on any arterial street… B. Trucks may operate off of arterial streets only for the delivery and pickup…”

That seems to solve the dilemma for “trucks”, which are defined by 36-82, but it explicitly says buses (or RVs) are not trucks, so I have no idea how/if/where 8.5′ buses/RVs are allowed.

I’m also not sure how to parse the RV exception (the large, so-called “Class A” RVs are 102 inches plus mirrors).

Some AASHTO Reference Widths

These are design/reference vehicle widths — presumably without mirrors.

AASHTO SU unit of 8.5 feet; see table 1, AASHTO Single Unit Truck and Single Unit Bus; Large School Bus Design Vehicle Dimenions.

I can’t find the AASHTO “Green Book” but here is some extracts dealing with turning radius of various design vehicles; the diagrams list the width. For example:
P – Passenger car – 8′
BUS-12 , BUS-40 – Intercity Bus – 8.5′
CITY-BUS, A-BUS – city transit bus, articulated city transit bus – 8.5′
S-BUS-12 – large School Bus – 8′
WB-14 (WB-40) – Intermediate semitrailer – 8′
WB-15 (WB-50) – Intermediate semitrailer – 8.5′
WB-19 (WB-62) – Interstate semitrailer – 8.5′
MH – Motor Home – 8′


Federal Size Regulations for Commercial Motor Vehicles

There are no surprises here, other than to note that federal regulations (laws?) require states to allow access to the NN (National Network), as long as they meet certain size standards, the width being no more than 102″ (2.6M) “excluding mirrors and certain other safety devices”. The NN is something like interstate and any federal aid highway, along with “reasonable” access to/from.

See Federal Size Regulations for Commercial Motor Vehicles from USDOT, FHWA.

ARS §28-1093. Vehicle width; exceptions

A. Except as otherwise provided in subsections B and C of this section and section 28-627, the total outside width of a vehicle or the load on the vehicle shall not exceed eight feet.
B. If pneumatic tires, in substitution for the same type or other type of tires, are placed on a vehicle in operation on July 1, 1950: <snip>
C. A person may operate a vehicle with a total width of the vehicle or the load on the vehicle of not more than one hundred two inches, exclusive of safety equipment, on:
1. Any segment of the national system of interstate and defense highways.
2. Any other qualifying federal aid highway.
3. Any state highway, as designated by the director.
4. Streets that are designated by a local authority as follows:
(a) The local authority may designate the streets by signage of the allowable streets or by maintenance of a map or list of allowable streets as approved by a resolution of the local authority.
(b) In designating the streets, the local authority shall consider any reasonable restriction including such safety restrictions as structural hazards and street width and any other safety factors identified by the local authority as a hazard to the motoring public.
5. A highway that reasonably accesses interstate system highways, federal aid highways or state highways from terminals and facilities that provide food, fuel, repairs and lodging or from emergency medical facilities.
D. Notwithstanding subsections A, B and C of this section, the total outside width of a noncommercial recreational vehicle as defined in section 41-2142 may be more than one hundred two inches if the excess width is attributable to recreational vehicle appurtenances that do not extend beyond the exterior rearview mirrors of the recreational vehicle or tow vehicle and the rearview mirrors only extend the distance necessary to provide the appropriate field of view for the vehicle before the appurtenances are attached. For the purposes of this subsection, “recreational vehicle appurtenance”:
1. Includes:
(a) An awning and its support hardware.
(b) Any appendage that is intended to be an integral part of the recreational vehicle and that is installed by the manufacturer or dealer.
2. Does not include an item that is temporarily affixed or attached to the exterior of the recreational vehicle by the vehicle’s operator for the purpose of transporting the item from one location to another location.

§28-956. Mirrors
A motor vehicle that is constructed or loaded in a manner that obstructs the driver’s view to the rear of the vehicle from the driver’s position shall be equipped with two mirrors located in a manner to reflect to the driver a view of the highway for a distance of at least two hundred feet to the rear of the vehicle.

UVC 14-103-Width of vehicles

(a) The total outside width of any vehicle or the load thereon shall not exceed eight feet, except as otherwise provided in this section.

(b) Incorporated cities and municipalities may by ordinance permit the operation within their respective jurisdictions of any motor bus or trackless trolley coach with a maximum outside width of not to exceed 102 inches.

(c) No motor bus or trackless trolley coach exceeding a total outside width of 96 inches shall be operated on any highway outside of an incorporated city or municipality, except that in suburban areas adjacent to municipalities any motor bus or trackless trolley coach with a total outside width of not exceeding 102 inches may be operated upon any highway route or routes having traffic-lane widths of not less than 12 feet.

(d) Subsection (a) does not apply to any vehicle being operated on a highway which is part of the National Network or which has been designated under 14-102 (b) as a National Network access route. The total outside width of any vehicle operated on such designated routes shall not exceed 102 inches.

(e) Subsection (a) does not apply to a vehicle being operated by a household goods carrier or to a vehicle which is part of a combination consisting of one semi trailer not exceeding 28 feet and six inches in length and a truck tractor under the following circumstances:

1. The vehicle is operating on a highway which is a reasonably direct and safe route to a scheduled point of loading or unloading for the vehicle; and

2. The vehicle is operating on a highway with traffic lanes which are at least (10) feet wide, if such highway is available; and

3. The vehicle is not prohibited from using the highway by official traffic-control devices; and

4. The total outside width of any such vehicle does not exceed 102 inches.


2 thoughts on “Width of Vehicles”

  1. Related Factoids: In CA
    CVC 35109. Lights, mirrors, or devices which are required may extend beyond the permissible width no more than 10 inches on each side.
    35100. (b) Safety devices shall not be included in the calculation of width.

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