Changes to the HCM
As a committee we work very hard to ensure that the Highway Capacity Manual is
error-free. When errors are identified, the Committee takes action to correct them
as quickly as possible. This page documents those efforts.
What to do if you have a question
- First, we recommend that you visit the TRB web
board and post your question,
- Second, if you don't receive satisfaction, you may contact the
Chair of the User Liaison committee with your
question or comment.
Definitions
The committee has defined the following types of changes, in order of impact to the
HCM:
Clarification: An explanation of what was intended in the HCM
Correction: A change in the HCM's written material to be more consistent with
the Committee's original intent (also called "errata")
Minor Change: A change in the HCM that is different than the Committee's
original intent, but does not involve new parameters
Major Change: A change in the HCM that involves new parameters or procedures
HCM Maintenance Procedures
(adopted July 2001)
(PDF version)
1. At any given time, the "official" HCM procedure for a given type of
facility will be the procedure published in the current version of the HCM, with the
approved interpretations, errata, and changes published on the website.
2. The User Liaison Subcommittee will maintain a written record of
interpretations/updates of the HCM to back up the material posted on the website.
3. The committee encourages chapter subcommittees to submit any interpretations,
corrections, and minor changes that would improve the definition and/or accuracy of an HCM
procedure. (Interpretations, corrections, and minor changes, and major changes are defined
in the HCM Maintenance White Paper dated June 2001).
4. Major changes proposed by a chapter subcommittee should be submitted to the full
committee for consideration rather than to the User Liaison Subcommittee. (The decision of
whether to publish a major change on the website or in the next version of the HCM should
be made by the full committee on a case by case basis.)
5. After the committee has acted on a policy for maintenance of the HCM, the policy
should be communicated to users of the HCM by various means, including email and regular
mail. After this one-time notice, users of the HCM will be expected to check the website
for clarifications, corrections, and changes.
6. In order to better document changes in the HCM, the committee should encourage
software developers to identify different versions of the software for each chapter by
date. The date associated with the software would indicate that all changes to the HCM
published through that date were incorporated.
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