Adam, you may be thinking of the iRAP Risk Factors (Google iRAP road attribute risk factors intersection type) which gives the relative risk at protected and unprotected right turns. The 80% reduction figure you quote appears in US data, e.g. Minnesota DOT summary of data currently online that goes back a bit (
MDOT Safety Programs Unit - Crash Reduction Factors October, 1986; Selection Process for Local Highway Safety Projects - Transportation Research Record 847, 1982;UKTRP - 85-6, University of Kentucky; March, 1985. ) These old data tend to hang around a long time and become gospel.Without doubt, removing turning vehicles from the through lane would reduce tail-end crashes but I can't vouch for an 80% reduction.
You could try contacting the iRAP people to discuss their sources.
Good luck!
Ray
Editor, Road & Transport Research
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Ray Brindle
ARRB Group
Malmsbury VIC
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Original Message:
Sent: 09-10-2014 21:17
From: Hugh Dixon
Subject: rear end crash statistics
Hi Adam,
One place that may help (not showing the science / statistics / working, but a reference none the less) is the black spot funding crash reduction factors.
I do these in Victoria and South Australia, but not in New South Wales, so cannot pinpoint where RMS has the information, but it should be there!
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Hugh Dixon
Senior Traffic Engineer
HDS Australia
Glen Waverley VIC
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Original Message:
Sent: 08-10-2014 22:23
From: Adam Mularczyk
Subject: rear end crash statistics
G'day
I read some time ago that the likelihood & severity of a rear end crash at a BAR type intersection is far greater than that of a CHR type intersection.
I recall (sounds very high) that there is over a 50% greater chance of having a rear end crash at the BAR intersection than a CHR intersection.
I have searched again for this paper but haven't had any luck.
Is anyone aware of such statistics as I am trying to push a road safety point & would much prefer a CHR (even with reduced design criteria as per the EDD of Austroads) rather than have a BAR type intersection.
Thanks in advance.
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Adam Mularczyk
Team Co-ordinator Development Engineering
Wyong Shire Council
WYONG NSW
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