CRF (AMF) for protected phasing?

[ACtrafficengr]

Looking at the literature available on-line, I haven't been able to find a crash reduction factor for changing from permitted/protected left turns to protected only phasing.

The closest I could find was from Kentucky, which listed CRF's for going from no left turn phasing to protected/permitted (10% overall, 40% left turn crashes), and going from no left turn phasing to protected only (20% overall, 70% left turn crashes).

Then again, NCHRP 500v12 states "a consensus on the extent of this effectiveness has not been reached," so should I just fall back and punt?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[jeremyk55]

Maybe this will muddy the water a little more. These numbers are from a presentation by Fred Ranck of the FHWA Resource Center at the 2006 KyTC Partnering Conference.

Add left turn phase 23-48% total, 63-70% lt turn

Add prot/perm. phase 4-10% total, 40-64% lt turn

Although these aren't exactly what you where looking for, they show the variability of the percentages you found.