6.2 Address Numbering Conventions & Even/Odd Sides

Why Address Numbers Are Their Own Skill on CritiCall

A dispatcher spends far more working time with house numbers than with a compass. Callers give street addresses instead of intersections, CAD (computer-aided dispatch) systems auto-populate response zones from address ranges, and officers radio in locations as bare numbers. CritiCall's Map Reading module tests whether a candidate can extract two things from an address alone, without seeing a full map: roughly how far away something is, and which side of the street it sits on. Both skills come from the same underlying convention — the block-and-parity numbering system used by most gridded U.S. cities, counties, and townships.

The important exam trap to understand up front: the specific convention (which side is even, which direction numbers increase) is not universal and varies by city, and even within a single metro area. Because of this, CritiCall items always state the convention directly in the problem ("Even addresses are on the west side of Mill Pike, odd on the east") rather than expecting a candidate to know one fixed rule. The skill being measured is applying a stated rule accurately and quickly — not memorizing "even is always north" as a universal fact, because it isn't one.

Core Terms

• Baseline — a reference street or point (often a main street or the historic center of a town) from which address numbers begin counting, typically at 0 or 100.
• Block — the address range between two consecutive cross streets. In the large majority of U.S. gridded cities, each block spans approximately 100 address numbers (the "100 block," "200 block," and so on), even though the physical block length in feet varies from city to city.
• Parity / even-odd side rule — the convention that assigns even numbers to one side of a street and odd numbers to the other side, so that knowing an address's last digit also tells you which side of the street to look on.
• Quadrant prefix — a letter code (N, S, E, W, or NE, NW, SE, SW) attached to a street address that identifies which quadrant of a city the address falls in, used because a single street name can run through multiple quadrants with entirely separate, non-overlapping address ranges.

Estimating Distance from Address Numbers

Because each block typically represents about 100 address numbers, subtracting two addresses on the same street and dividing by 100 gives a fast estimate of how many blocks apart they are:

This is exactly the kind of quick mental math CritiCall's Map Reading and Numerical Ability modules both draw on: a caller who says "I'm at 1900 Grant, the fire is at 2300 Grant" has effectively told the dispatcher the fire is roughly four blocks up the street, before anyone even pulls up a map.

Applying a Stated Even/Odd Rule

When a problem states a parity convention, treat it as a two-step lookup: first identify whether the target address is even or odd, then apply the stated side.

Worked example: A dispatch note reads, "On Sunset Boulevard, even-numbered addresses are on the north side; odd-numbered addresses are on the south side." A caller reports a break-in at 4521 Sunset Boulevard. Because 4521 is odd, the stated rule places the address on the south side of Sunset Boulevard — a unit should be directed to approach from the south side of the street specifically, not simply told "Sunset Boulevard" with no side specified.

Quadrant trap: A caller says an incident is at "800 Park Avenue." The CAD lookup returns two matches: 800 NE Park Avenue and 800 SW Park Avenue — an identical street name and number, but on opposite sides of the city, possibly miles apart. The correct action is to confirm the quadrant before dispatching, never to assume one is "probably" correct. This is one of the highest-consequence traps in the entire Map Reading module, because guessing wrong sends a unit in exactly the wrong direction across town while an emergency waits.

Combining Distance and Side in One Item

CritiCall's harder address items ask for both pieces of information at once — distance and side — in a single scenario, which is why it helps to work through them in a fixed two-step order rather than trying to picture the whole street at once.

Worked example: A dispatch note states, "On Redwood Avenue, even-numbered addresses are on the north side and odd-numbered addresses are on the south side." A unit currently sits at 1800 Redwood Avenue (north side) and is reassigned to a call at 2300 Redwood Avenue. Step one, distance: 2300 minus 1800 is 500, or about 5 blocks. Step two, side: 2300 is even, so the call is also on the north side — meaning the unit continues up the same side of the street it is already on, rather than crossing over. Answering only one half of a combined item (getting the block count right but missing the side, or vice versa) is a common way candidates lose points on this section even when their arithmetic is correct.

This same two-step habit — distance first, side second — also carries directly into the jurisdictional-boundary items covered later in this chapter, where an address's parity determines which agency responds rather than which side of a street to approach from.

Common Traps

• Assuming a universal even/odd rule ("even is always north") instead of reading the rule stated in the specific problem.
• Treating the ~100-per-block estimate as an exact distance rather than an approximation — physical block lengths vary.
• Ignoring a quadrant prefix, or assuming it can be inferred, when two otherwise identical addresses exist in different quadrants.
• Answering a combined distance-and-side item with only one part correct — both the block estimate and the side determination must be checked separately.