The Institute of Transportation Engineers' just published a Recommended Practice report titled Transportation Impact Analyses for Site Development. This is an update to the PROPOSED Recommended Practice published in 2006. Both reports are worthwhile references for anyone involved in preparing traffic studies.
The new version has the same table of contents and is the same length as the previous version. I looked closely at all of the tables and figures, comparing each version side by side. The only changes appear to be updating references to the Trip Generation report to the 8th Edition published in 2008 (hence the minor tweak to Table 2-2). I believe all of the other tables and figures are consistent between the two versions.
If you own the Proposed Recommended Practice, don't waste $35 buying the new version. Simply cross out the word Proposed on the cover and replace Table 2-2 with the update below.