33 CFR § 164.40 - Devices to indicate speed and distance.

---
identifier: "/us/cfr/t33/s164.40"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "33 CFR § 164.40 - Devices to indicate speed and distance."
title_number: 33
title_name: "Navigation and Navigable Waters"
section_number: "164.40"
section_name: "Devices to indicate speed and distance."
chapter_name: "COAST GUARD, DEPARTMENT OF HOMELAND SECURITY"
subchapter_number: "P"
subchapter_name: "PORTS AND WATERWAYS SAFETY"
part_number: "164"
part_name: "NAVIGATION SAFETY REGULATIONS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "46 U.S.C. 2103, 3703, 70034; E.O. 12234, 45 FR 58801, 3 CFR, 1980 Comp., p. 277. Sec. 164.13 also issued under 46 U.S.C. 8502. Sec. 164.46 also issued under 46 U.S.C. 70114 and Sec. 102 of Pub. L. 107-295. Sec. 164.61 also issued under 46 U.S.C. 6101. DHS Delegation No. 00170.1, Revision No. 01.4."
cfr_part: "164"
---


# 164.40 Devices to indicate speed and distance.

(a) Each vessel required to be fitted with an Automatic Radar Plotting Aid (ARPA) under § 164.38 of this part must be fitted with a device to indicate speed and distance of the vessel either through the water or over the ground.

(b) The device must meet the following specifications:

(1) The display must be easily readable on the bridge by day or night.

(2) Errors in the indicated speed, when the vessel is operating free from shallow water effect, and from the effects of wind, current, and tide, should not exceed 5 percent of the speed of the vessel, or 0.5 knot, whichever is greater.

(3) Errors in the indicated distance run, when the vessel is operating free from shallow water effect, and from the effects of wind, current, and tide, should not exceed 5 percent of the distance run of the vessel in one hour or 0.5 nautical mile in each hour, whichever is greater.

[CGD 83-004, 49 FR 43467, Oct. 29, 1984, as amended by USCG-1998-3799, 63 FR 35532, June 30, 1998]