TOPICS
Surface
Dressing
Highways
Agency, DMRB Skid Testing
Road
Surface / Tyre Generated Noise
Motto
of the Month
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Introduction
It is my birthday this month, just two years to go before I retire
at 60, unless the government, or the local authority have some other
devious plan.
It is a shame that I am "kind of" counting down, but the highways
maintenance world is now a very different place to that which I have
worked in all my life, and I cannot say it that has changed for the better.
Not in what needs to be done you understand, but how people want to
provide the service.
I sometimes wander if the industry is trying to become a self
sustaining entity, rather than have the construction and maintenance of
a safe, durable, free-flowing highway network as the prime
consideration.
I see lots of bits of paper describing lots of new management
arrangements, new specifications and procedures, and wonderful
new materials, yet I see more and more problems arising all around me,
nationally and increasingly locally.
I think it is time for me and my kind to bow out and leave it to the
marketeers.
I just hope "they" can persuade the government to give them
all that extra money they keep asking for, because in my opinion the budget they are
currently receiving will not
suffice with the new way of doing things.
But the good news is, soon, it will no longer be my concern.
Surface Dressing
If you have not finished surface dressing yet you should have, and if
you are laying anything bigger than a 6mm. chipping you had better
start praying to the god of surface dressing that it will be a mild winter.
And if you think you are being clever by increasing the rate of spread
of binder you had better hope it is a cool summer again next year.
The correct surface dressing design is the correct surface dressing
design and should not be "tweaked".
Do not judge the success of this years surface dressing until after
the winter and the first genuine hot spell of next summer, what looks
good now may disappoint by this time next year.
I wonder if/when we will be getting a new Road Note 39 to take in to
account the change in surface dressing chipping sizes, nobody seems to
be too bothered.
Highways Agency
(DMRB)
The new Highway Design Note HD 28/04 Skid Resistance was published in
August, you are able to obtain a copy from the excellent website
provided by the Highways Agency that allows you to download the
majority of the Design
Manual for Roads and Bridges (DMRB), "online", all
15 volumes of it.
This is a comprehensive resource of information in .pdf format,
that is presented in a straight
forward manner and is easily downloaded in sensible sized
files.
I make many references to this manual throughout my
website, in particular Volume 7, and you are able to access this volume and its sub-sections for
further information on a particular subject.
You really should visit this site if only to make
yourself aware of the depth of information that is
available to you.
It is of particular relevance to
those of you who deal directly with Highways Agency
funded work, but the information it contains is such that it is valuable
to all involved in highways maintenance and construction.
I am not sure whether this Design Manual will exist in its present
form after the "new" Specification for Highway Works is
published shortly. If it does I would imagine at least some sections
will have to change significantly.
It might be well worth a browse to download the design guides that
contain good general information on the many aspects of highways
maintenance and construction (mostly Volume 7) that it contains, just
in case they dissappear.
Road
Surface / Tyre Generated Noise
 I will be brief with
this item. It is just to mention that I am very disappointed in the
glib way that "new" road surfaces are claimed to reduce tyre
generated noise. The road surface does not generate any noise itself,
but it does contribute to the noise generated by vehicle tyres.
The claimed reductions in noise levels in db(A)'s with some
"new" surfaces is quite phenomenal.
In some articles I have seen claims ranging from 5.5 to as much as
10.0 db(A)'s, compared with what I have no idea, the articles did not
say. It must be some particularly "noisey" overchipped hot
rolled asphalt or poorly textured length of concrete carriageway
specially retained for reference purposes.
It would also be nice to know how these noise levels were
measured.
The organisation I work for have been conducting surveys to compare
tyre noise generation from various road surfaces using TRL and Triton
for three years, and the results we have obtained have been most
enlightening as to what the true situation is when comparing the contribution
the road surface makes to tyre noise generation.
I am sure TRL would be most willing to undertake similar surveys for
other organisations.
The Highways Agency were the first to commission such surveys, but
it appears the
results are still waiting to be published.
The public are not fools, telling them a road surface will reduce
noise levels will not make it so, unless the existing road surface has
particularly high noise generating characteristics, which is the case
on only a few well publicised sites that are not receiving a noise
reducing surface for various reasons, well not yet, allegedly in the
future it will happen.
What I can convey without giving away too many secrets is that it
appears for all bituminous road surface types, that if you reduce traffic speed
from 80kmph to 50kmph you will genuinely reduce tyre generated noise
by around 6db(A)'s, which is significant.
Whether this speed restriction will be tolerated by the motoring
public in noise sensitive areas remains to be tested, but in some
residential urban areas adjacent to high speed roads I would have
thought it worth a try.
It would certainly be the most cost effective method of reducing noise
levels.
Oh, and a little more work on developing tyres that generate less
noise would be nice, especially as "super singles" now
appear to be the predominant choice of tyre on heavy goods
vehicles.
Motto of the Month
"Common
sense is not so common"
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