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Safety Slide Range Finder
Type B car safeties: the allowed stopping distance (slide) for the
governor tripping speed in front of you — A17.1 Table 2.17.3 verbatim, with the §8.2.6
formulas answering between the printed rows.
Inputs
Pick the safety type and enter the tripping speed.
Pre-1955 installation. These formulas are the
A17.1-1955-and-later requirement, read in A17.1-2022 and reported constant across editions
since 1955. An installation older than that, or one governed by A17.3 questions, gets its
range from the book for the edition that applies — not from this page.
You are on the 700 fpm row. A17.1-2022
prints max = 128 in. here, but the standard's own §8.2.6 formula gives 118.2
in., and the SI column of the same row (2 950 mm ≈ 116 in.) agrees with
the formula. The printed figure appears to be the standard's own typo. This page shows the
printed value because the printed page is what an AHJ holds up — but know both numbers
before you judge a mark between 118 and 128 inches.
Reference table — A17.1-2022, Table 2.17.3 (imperial), verbatim
Rated speed → the maximum governor trip speed
permitted for it, and the slide range at that trip speed, in inches as printed. If you
measured the actual trip speed (the governor calculator makes
that number honest), enter it above instead — the range belongs to the trip speed, not the
rating.
| Rated speed, fpm | Max governor trip, fpm | Min slide, in | Max slide, in |
|---|
* printed 128; the
standard's own formula gives 118.2 and its SI column agrees with the formula — see the
note that appears when this row is used.
The formulas (A17.1 §8.2.6, read verbatim). Min slide
S′ = V²÷231,840 ft (a 1.0 g average stop — any shorter and the safety slammed harder than
the code allows). Max slide S = V²÷81,144 + 0.84 ft (a 0.35 g average stop plus wedge
travel — any longer and it isn't gripping). V is governor tripping speed in ft/min.
§2.17.3 says the table IS these formulas; between printed rows the formulas answer
directly, and this page says which answer it gave you.
What this range applies to. The requirement is the safety
stopping the car with rated load, from governor tripping speed — the acceptance test
(§8.10) and the Category 5 periodic test (§8.6.4.20). On a no-load Category 1 slide
(§8.6.4.19) the car is lighter and stops shorter; how to read a no-load mark is A17.2's
territory and your judgment, not this page's. Pass/fail comes from the book — this page
makes the arithmetic honest, it does not sign anything.
⚠️ Adam — one eyeball left, then this box can go: everything
numeric on this page was read in your A17.1-2022 copy on 2026-08-01 — Table 2.17.3
from the rendered page image (book p. 82), the §8.2.6 formulas verbatim (book p. 303). What
remains is yours: open p. 82 and confirm the 700 fpm max really prints 128 (the
anomaly note above), and note that Kansas/Missouri adopt specific A17.1 editions —
if your AHJ adopts something other than 2022, spot-check a row in that edition. The
requirement is reported constant since 1955, so expect no difference; expecting is not
checking.