Good Afternoon,

AS an Ex-TRL, EX-AA Foundation researcher now on Yr III of a PhD
investigating the dry frictional properties of these materials, I would
be interested in any observations group members may have on these
materials, so long as the observations are based on fact (ie. from
measurement) rather than assumption and conjecture!

Sincere Regards

John "Fatbloke" Bullas

Transportation Research Group
University of Southampton

Colleagues

Since there is a potential for stopping distances in the dry to be
extended by up to 46% for vehicles not equipped with ABS with these
surfaces (Derbyshire Police presentation 2001), I thought this thread
might be of interest, but maybe stating this fact would have been a
good thing to do firstly!!!

If you are interested in road safety and an active highway engineer you
might want to read my paper on the subject and get back to me
(johnb-at-soton.ac.uk... anonymously quotable or not

see: http://tinyurl.com/ac65x (PDF)

Devon routinely grit their new roads during construction (with 3mm
quartzite) and this has been shown to deliver good skidding resitance
in the wet on day one! A few other counties are beginning to grit since
in Germany these materials are always gritted on construction, this
fact was known about when we first started using them but sadly not
adopted or assessed

The Dutch had real problems (discovered in 1991) with slippery porous
asphalts ( most of it was slippery in the dry for at least 4 months
"from new"), this was reported on in 1997 (European Conference on
Porous Asphalts) and at SURF 2004 in Canada

In 1986 13 were killed on a stretch of the M4 with low dry friction (
over tarred pre-coated chippings) and sub standard crash barriers

Dorset have reported approx 30% of their new SMA surfacing doesn't meet
the minimum requirements for skidding resistance in the first year of
laying:
http://tinyurl.com/8p9up (PDF
report)

The highways agency have recently released details of research they
have been funding:

http://www.highways.gov.uk/news/articles/15068893.htm

"The report makes four recommendations and the agency's planned
research programme already covers work to address the first with the
work due to be completed in late 2006."

The report will make interesting reading!

I look forward to your learned feedback, the "bituplaning" effect can
occur at 30mph!

Regards

John