GIS/LIS (1994), p322-331, copyright GIS/LIS
The County of Los Angeles (LAC) and its adjacent public agencies use at least sixty (60) different house numbering systems (HNSs) to assign addresses to streets and buildings. An unknown number of private house numbering systems assign addresses to commercial complexes, mobile home parks, and gated tracts. Other addressing systems locate callboxes along freeways, mileposts along highways and railways, stations along rivers and flood channels, aqueducts, pipelines, or power lines. The use of so many HNSs leads to many duplicate street names and address ranges, which complicate the construction of address reference file and automated geocoding. This document is an initial inventory and technical description of the County's publicly-maintained HNSs, including an HNS attribute table useful for the automated editing of topological address reference files such as TIGER.
This work came out of the need to rigorously edit house numbers in address reference files for County geocoding use. It is driven by the perceived inadequacies of the house numbering data in topological reference files, difficulties in using geocoding software (there are, to name but a few, 20 First Streets, 7 First Avenues, 12 Main Streets, 13 Broadways, 15 California Avenues, 10 Orange Avenues, 4 Los Angeles Streets and 4 Spring Streets in the County), and the lack of any consistency in government or private reference file content and construction where address assignment systems meet and overlap and street names and/or address ranges are duplicate. The results of these meetings, overlaps, and duplications may appear to be errors in reference files when they are not, or may mask real errors in the reference files, and may lead to false matches in geocoding.
DEFINITIONS--This guide uses the following terms as specified:
An address in general is a phrase denoting a location.
An addressing system is a convention (a set of rules) for assigning addresses along a transportation network such as streets, freeways, or railroads. Addresses in this context may be almost anything that identifies a point along a segment: house numbers, callbox numbers, mileposts, stations, block/lot numbers, and post office box (POB) numbers.
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A house numbering system (HNS) is a convention (a set of rules) for the assignment of addresses to buildings, residences and occupancies.
A house numbering scheme is a convention for using one or more house numbering systems at a particular place, such as a community or city.
The distinction between house number scheme and house number system is central to explaining the house numbers used for urban dispatch, mailing, voter registration and navigation. While most house numbering schemes use the same house numbering system (one single point of origin) for east-west streets and for north-south streets, some schemes use different systems for east-west streets than for north-south streets. For example, the Beverly Hills house numbering scheme uses the County (west) numbering system for its east-west streets, and its own Beverly Hills numbering system for the north-south streets. About 50 other communities, whether incorporated or not, use multiple numbering systems in their numbering schemes.
The owner of a house numbering system is that agency which has the authority to set or assign an address (house number) within that jurisdiction. In general the planning, engineering, or the building and safety agency of a city or county assigns house numbers in its jurisdiction, and on occasion may change them. A city may contract those services out to a county agency, so that a county agency assigns numbers in lieu of the jurisdictional city; about fifteen cities do so in Los Angeles County. This means that there is no easy correspondence between house numbering systems and address-assigning agencies. If the boundaries of an HNS are congruent with those of the legally empowered agency, (e.g. many small cities), then for example the City of Santa Monica and only that City assigns house numbers in Santa Monica HNS. Inglewood and Torrance are examples of Cities with local numbering systems that annexed surrounding developments numbered with the County numbering system, and did not renumber the annexations: now those Cities assign addresses using two different numbering systems within their city limits. Likewise the City of Los Angeles did not renumber the former cities and communities it annexed, so that today it uses, in addition to the Los Angeles County HNS, the San Pedro, Venice, Wilmington, Pacific Palisades, and Eagle Rock/Highland Park house numbering systems. And Los Angeles County itself assigns numbers according to many local numbering systems, rather than forcing conformity with its own system. Montrose is an example of an unincorporated community (i.e. where a County agency assigns house numbers) that uses an adjacent city's numbering system, in this case the City of Glendale's.
The transition or borders between numbering systems and schemes may be so smooth that they are barely noticeable, e.g. in Lomita where Wilmington west numbers on Pacific Coast Highway transition into County west numbers. Transitions may be jolting and confusing, as in West Covina where five-digit County east numbers are found on one side of the street facing four-digit west numbers on the other side. On the next block the four- and five-digit numbers may be reversed,
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depending on the boundary between unincorporated County and the City of West Covina, which changes every block or so.
Directional house numbering is a very old idea. Some Roman cities were gridded and numbered for more than thirty kilometers out from their civic center. In general a city would establish some recognizably important point as the source from which house numbers would be assigned, with the numbers increasing with the distance from the origin. In a world of rectangular gridding it is convenient to assign a direction to the numbers so that they increase in a cardinal direction (e.g. north, south, east and west). The line that separates the north from the south numbers is termed a baseline. The east-west divider is the meridian. For very large numbering systems the baselines and meridians may be a complicated succession of streets, rivers, freeways, city limits, etc., chosen as the dividing line (Marr, 1969). Often, but not always, the baseline of a numbering system intersects its meridian forming a physically locatable origin. Most of the HNS systems inventoried here have intersecting baselines and meridians with locatable origins, but there are exceptions. In some systems the baseline and meridian do not physically intersect, or do so only if theoretically extended. For example, the County of Orange's northern system (it has three systems) uses a township line that forms the northern most boundary of the County as its baseline and the westernmost range line as its meridian. These two axes intersect only if extended well into Los Angeles County, somewhere in the City of Downey.
House numbers referenced to the baseline and increasing to the north are referred to as "north numbers" and similarly for the other directions. The use of baselines and meridians may generate quadrants. Some numbering systems do not use all of the available directions; the baselines and meridians may be chosen so that all of the numbers are in one quadrant, e.g. south and east, or north and east, etc., of the origin. This arrangement is typical of beach cities adjacent to the coastline, but is not unique to them. For example, the California County Freeway Callbox numbering system uses only the north and east quadrant. Callbox numbers in California are referenced to either the western County border (e.g. the coast) for nominal east/west routes or to the southern border of each county for north/south routes. All callbox numbers are north and east irrespective of actual geographical direction of travel on a freeway.
Directional numbering systems presume an orientation, or azimuth, of the entire system. Although the nominal "North" direction is north, it may be tilted either east or west from due north. The orientation of a particular HNS we refer to as the azimuth of that system; it is determined by picking a representative street (perhaps a baseline) and measuring its orientation. Usually, but not always, the NS and the EW streets intersect at right angles, so the azimuth of the EW numbering system is perpendicular to that of the NS streets. Sometimes the baseline and meridian may be rotated so much that the numbers are termed "southeast" and "southwest" numbers. The logical assignment of directionality is independent of the geographic azimuth of a street segment.
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Some addressing systems are not referenced to any cardinal direction. Rather, they reference a local point of origin and simply increase away from that point. We call these systems linear numbering systems; examples include mileposting and stationing. Mileposts are measures of length denominated in land miles along the centerline of a linear feature such as a highway, a railroad, or a pipeline. Stationings are measures of length along the centerline denominated in hundreds of feet. Both mileposts and stationings use an "nnn+00" convention for display. For mileposts this is the number of miles+hundredths of a mile, and for stationings this is increments of hundreds of feet+feet. Railroads, pipelines, and rivers as well as roads without house numbers (e.g. freeways and rural roads), are often addressed with linear systems.
Occasionally a house numbering system appears to be linear rather than directional. The City of Bradbury uses two house numbering schemes. A small part in the southeast corner of the City of Bradbury abutting the City of Duarte, uses the Monrovia HN scheme. Elsewhere the City of Bradbury uses house numbers which increase away from the "beginning" of each street. Elsewhere, some rural systems, especially in mountains, use a linear system based upon miles + hundredths with no decimal, i.e., 1026= 10 miles and 26/100, from an origin along a major (or at least paved) road as the numbers.
The City of Rolling Hills appears to assign its house numbers in the order that residences are built. This is known as order numbering (where the order in this case happens to be chronological); navigation may be difficult to the uninitiated.
Many house numbering systems are quite strict about parity: opposite sides of the street should have all odd or all even numbers. In the County, the dominant convention is that "the north and west are odd". This means that the west side of north/south streets, and the north side of east/west streets, are assigned odd numbers. Not all systems agree with this convention.
In Los Angeles County there are some notable exceptions to the "north and west are odd" convention: a few of the local numbering systems which differ are: Avalon, Montebello, San Pedro, Santa Monica and South Pasadena. They switch one parity or the other: see Table 1 for the odd side designations. Another common exception to the parity convention is "nipple streets", i.e. short cul-de-sacs that are numbered as if they were one side of a larger street, leading to both topological sides of the segment showing the same parity and increasing in opposite directions. Nipple streets may or may not have the same street name as their "parent" street; sometimes they keep the same street name with a different street type.
Street names are made of "components" and "names". Components are typically "street type" and "street direction". "Street direction" usually means the directionality of the street numbering. Often on streets where the house numbering scheme is
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entirely in one quadrant of the address alignment system the street direction is omitted, especially by the US Postal Service Zip+4 reference files. Where the address scheme uses more than one quadrant the street direction is usually included in the full street name. However, a direction may be part of the street name and may not indicate the numbering direction. It is not always self-evident whether a direction in the street name refers to the numbering direction or is part of the street name; consequently address parsing routines may make errors - usually when the direction is part of the street name.
Often if a direction is not the directionality of the numbering system, it is placed contrary to the prevailing naming convention of the local streets, either after or before the street name. For example, if the dominant naming convention is "Dir/Name/Type", (e.g. "W. Venice Blvd"), a direction that is not denoting the numbering will be placed after the name, e.g. "Venice Blvd North", as is the case in the community of Venice where east/west Venice Blvd is split into two parallel roadways with housing and parking lots in the median between them. This contrary placement is also true where the dominant naming convention is "Type/Name/Direction". A striking example of a direction representing the street name and not the directionality is Palos Verdes Dr N/S/E/W in the Palos Verdes Peninsula. This street circles around the Palos Verdes hill: the directions represent the street's position relative to the hill and not the direction of the house numbers.
Some street segments carry house numbers from two different HN systems (TIGER files makes provision for this with the Tiger 6 record). Dual numbering is rare in Los Angeles County, but it does occur on Palos Verdes Dr. E.
To implement these concepts in a geocoding system, one can create a table similar to Table 1 reflecting one's HNS boundaries, then use the table as a rule for editing house numbers in geocoding files and for address verification. The table contains attributes of the HNS polygons. The process might be as follows:
SEPARATE N/S FROM E/W POLYGONS -- At least two separate polygon layers representing house numbering systems are needed, one for north/south and the other for east/west numbering systems. Other address assignment systems (rivers, rail, freeways) could be given their own layer(s) if polygon coverage is desirable, but not all address systems need polygon or layer coverage.
OVERLAY N/S AND E/W FOR SCHEMES -- The overlay of the polygons for east/west on the north/south will represent the unique house numbering schemes in the County or area of concern. The overlays will show the areas where systems abut each other and could identify segments needing special attention because they are on boundaries. If overlays are developed first, the polygon attribute could cause or generate segment attributes. If segment attributes are developed first, they can be accumulated to generate the polygon coverage.
ASSIGN HN SYSTEM TO EACH SIDE OF EACH STREET SEGMENT -- Using a polygon overlay, each street segment may be assigned a house numbering system code attribute for each side. One suggestion Is a five-byte FIPS code plus a one byte direction code for each side (e.g., '08845S' is the Alhambra FIPS Code 08845 and (S) is direction south in the numbering system.) Using the convention
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proposed here, Palos Verdes Dr. W is numbered with Palos Verdes Estates south house numbers (55394S), PVDrN and PVDrS are numbered with Los Angeles County west numbers (99037W), and PVDrE is numbered (mostly) with Los Angeles County south numbers (99037S). Azimuth may be useful for automating the assignment of directionality to street segments within a HNS polygon.
USE POLYGON ATTRIBUTES TO EDIT ADDRESS RANGES -- The HN systems rules can be created from the HNS polygon attributes to be used in the edit checking of house number and direction data in a geographic reference file. Each segment is assumed to have a topological direction establishing the From- and To- nodes and which side is Left and Right. By convention, the topological direction may be assigned to coincide with the numbering direction (if the segment is not a border between HNS's). The edit routines can look for the many conditions ("twists", "flips" "splits", etc.) in the house number data, especially testing:
CREATE EXCEPTION CODES -- The geographic reference file may need some segment side exception codes to represent cases where a street segment fails the above tests, but the failure correctly represents an anomaly on the ground (e.g. Torrance with parity errors, Palos Verdes Drive East (PVDrE) with dual numbers, N. Sierra Hwy. with E/W house numbers, etc.). Other exceptions may included street segments that are addressed from another segment, such as (1) cul-de-sac "nipple" streets addressed off a larger street, (2) long and older driveways which are cut by newer streets but retain their older street numbering, (3) large buildings also numbered from other street(s) and (4) mobile home parks with internal streets but having with one street address at the gate for all units. These situations seem to call for a pointer to the other street segment actually used for house number assignments.
MISSING/UNKNOWN/NOT ADDRESSABLE -- It is believed that some of the existing reference file problems with missing, unknown, or not addressable street segment codes would be reduced by applying the solutions described above. As long as every segment is assigned to a house numbering system (and there is some regularity to the HNS), the computer can calculate what the address range should be when the side of the street is a wall, vacant lot, or the back side of other buildings. The range is still applicable even if the addresses cannot exist.
It is suggested that TIGER SDTS adopt similar standards rather than or in addition to carrying the proposed mass of edit-and-verify flags as proposed in the (Census, 1992: pg. 13: AP00 Record). The proposed edit-and-verify flags (fields LVPAREXC--LEOVLAPT, etc), when they are not reflecting bad data, may often reflect transitions between house numbering systems. For example, in the case where two sides of a street are numbered in opposite directions, it would be better to report that two sides of a street use different numbering systems rather than to report that an edit check failed and that this failure was field-verified. Also, table HNS table could carry address formatting data represented in the proposed Tiger SDTS POSClL--POSC4R fields rather than carrying it on every record as proposed.
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Table 1 contains the following fields:
FIPS CODE--The Federal Information Processing Standard (FIPS) -55 coding can be used to uniquely represent every publicly-maintained house numbering system. The FIPS 55 code was chosen after Zipcode and other codes failed to assign each house numbering system a unique code. For example, the Palos Verdes Peninsula with its three public house numbering systems defeated the sole PV zip (90274); Los Angeles City with its six house numbering systems defeated the others.
A county like Orange with its multiple numbering County systems might be encoded by using a Census Civil Division (CCD) code from the FIPS-55 table that has an appropriate name. For example,, Kern County's Los Padres numbering system is here assigned the Los Padres CCD code of '91770' (even though it is officially a Ventura County CCD). A different set of codes would have to be adopted for other kinds of addressing systems, e.g., private house numbering systems, river stationings, railroad mileposts, etc.
CLASS--Systems are divided into classes to identify the basic features being addressed, i.e., 'H' - House numbering, 'F' Freeway callbox. This table could include watercourses, railroads, power lines, pipelines, and their addressable features.
PLACE NAME-- The FIPS code place name.
COUNTY--A one-byte code of 'L' for Los Angeles, 'K' for Kern, 'O' for Orange, 'S' for San Bernardino, and 'V' for Ventura counties.
NUMBERING DIRECTIONS-- Four contiguous bytes encode the directions available in the address assignment system:
A code of 'N_EW' means the house numbering system assigns north, east, and west numbers, but it does not assign any south numbers.
ODD SIDE-- If an addressing system is directional and enforces parity on the sides of a segment, these two contiguous codes respectively represent the side of the nominal north/south (N/S), and east/west (E/W) streets that contain odd numbered addresses. Note that the Bakersfield system defeats this coding, since the parity of north/south streets switches depending on whether they are east or west of the meridian, which is Union Ave. A more comprehensives coding is needed to represent all possible systems, but this is not necessary for LA County's purposes.
BASELINE and MERIDIAN-- These are the transportation routes (e.g. a street) or legal features (e.g. a City or County boundary) that most closely identify where the
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north/south (baseline) or east/west (meridian) numbering begins for the particular addressing system.
APPROXIMATE EXTENT COMMENT-- The approximate extent of the house numbering system's use, a current guess as to the extent of a house numbering system.
THOMAS PAGE OLD/NEW-- The Thomas Brothers map book (a local map publisher), page number and grid coordinates as found in the old and new (digital) editions locating where the Baseline and Meridian intersect. For some addressing systems there are no TB pages available and/or no intersection of baseline with meridian.
AZIMUTH-- The HNS table includes four azimuths, one is entered for each of the existing numbering directions. If a particular HNS only recognizes EW streets, only their orientation is recorded. The listing, however, prints just one azimuth, either that of the N direction, the reverse of the S direction or the N perpendicular of the EW direction. Some HNS will have several street grids tilted in different directions (e.g. Burbank). If so, several azimuths are printed.
U.S. Bureau of the Census, 1992. TIGER/SDTS proposal, August 1992. Washington, D.C.
Corwin, Margaret, 1978. Street Naming and Property Numbering Systems, Report 332, (1978); published by the American Society of Planning Officials (ASPO) (312/955-9100). Report 332 reviews and illustrates both street naming and a staggering variety of numbering systems, providing a step-by-step program for reassigning house numbering in an area. The best document on the topic.
Los Angeles County Department of Public Works, 1983. Los Angeles County House Numbering Manual (July 1983).
Marr, George, 1969. The Right Address, in Los Angeles County Regional Planning Department's Quarterly Bulletin, No. 105, July 1, 1969.
State of Texas, 1991. Addressing Handbook for Local Governments (August 1991).
The author and the County Geographic Information Systems Advisory Body would like the thank the following individuals for their contributions and leadership: Wayne Bannister, George Boss, Vern Cowles, Craig Gooch, Linda Hull, George Marr, William Montgomery, Tom Peacock, Tim Smith, Jon Taylor, Cindy Wilson, and the Thomas Bros. Map Company.
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