cfsmtb <[email hidden]> wrote
in news:[email hidden]:
Quoted message said:
A lengthy article, but worth delving into over a cuppa or
lunch. π If you're a traffic engineer, it might be wise to
have a relaxing camomile tea handy before reading this. π
Didn't bother with the relaxing tea.... and this response is
longer I think (damn)
Monderman's approach actually isn't that new. If you look at
lower order surburban streets you'll see that the trend in a
Australia for narrower streets with less markings. Two
reasons, save space and to slow people down. Similar things
have been happening in the second order urban roads (close to
city centres etc) again to slow things down and make people
think. But.....
Remember that this will only work where things are reasonably
congested (or the environment is) and the traffic speed is
low.
Congested because if there is no outside monitor (other
traffic) people will tend to behave quite differently....
Slow because if you are moving much faster than 60km/h you
need some distance to react hence the signage for motorway
exits. Australia adopted European practice for this by the
way.
Traffic engineers have two competing priorities that govern
design (depending on road hierachy). One is safety the other
efficiency.
Monderman's approach is good for safety but if you string
several of his type of intersections together the traffic is
moving too slowly to be efficient (more enforced stops/slower
travel times). As you reduce side friction (bike lanes,
reduced property access, removal of parallel, parking
improved directional signage etc) your lane capacity
improves, travel times reduce (depends on intersections) and
efficiency increases. So does speed and your brain in
neutral effects.
Much of the signage/linemarking you see has less to do with
safety and more to do with efficiency. Monderman is
advancing an arguement to reduce efficiency to improve
safety. Possible if you have a good PT/cycle/ped network,
dense population and a population that accepts such things.
Our problem is the design of roads for peak hour not off
peak. In many regional centres and most fringe metro areas
you often find a need for 4 and 6 lane roads and traffic
signals to accomodate the peak flow. Outside of peak hour
though these roads have too much capacity leading to high
travel speeds etc etc.
This design philosophy comes about because of what the people
demand (or what politicians think the people want). Everyone
hates traffic jams so we design to minimise these. My
preference is to let congestion happen to force people to
consider alternative transport options or SLOW DOWN AND
THINK. It also impacts on housing choice.
If people face more congestion they will generally move
closer to work to minimise travel time. The current
situation in Australia is the reverse of this. We let people
move futher and further away from work centres and then
increase road capacity to maintain travel times therefore
justifying the sprawl.
The article contains some inaccuracies btw. The distribution
of traffic accidents follows a traditional "bell" curve with
regards to speed and/or volume. Most accidents occur at
speeds less than 60. What does increase with speed is
accident severity (or outcome).
Can we use Monderman's work here?
Propably not in total. Why - because Australians are not
Dutch or French or .......
The roundabout is, for many situations, an ideal intersection
treatment. It removes the potential for the most severe
intersection accident (headon), slows traffic down without
necessarily stopping it and can be designed to include peds
and cyclists. Works wonderfully in Europe and is a pack of
pooh tickets in Australia.
Australia's seem (horrible generalisation following) to be a
weird mix of passive/reactive. Australian politicians (and
solicitors) are also opposed to personal responsibility
(which Monderman's solution emphasizes) We don't want to
force ourselves on anyone (claim the lane) but react poorly
to a perceived infrigement of our rights. So everyone still
tries to give way to right at roundabouts and if you actually
follow the rules (give way to traffic on the roundabout)
you'll often be abused. Also the issue with accelaration to
the roundabout so that I have right of way (which you don't
ever). The same for cyclists that claim a lane on the
roundabout and drivers reactions to same.
The four way stop is another intersection that generally
doesn't work because no one want't to be the first to go
(butting in).
As a result we are designing roundabouts so large (30+m
centres) that approaching traffic does not percieve the
traffic on their right as a give way situation. People the
appear to follow the appropriate rule - give way if the car
is close enough to be dangerous (ie on the roundabout).
And all of this is why traffic engineering is extremely hard,
open to interpretation etc. It really isn't engineering in a
classic sense, it is behavioural science. I don't remember
having any courses on behavioural science when I was a uni.
Being engineers we study the problem and derive a statistical
solution. Problem is that people aren't statistics and vary
considerably between each town/state/country.
For example in Mackay if the Merge in Turn sign is on a merge
lane people seem to be able work out how to merge, take it
away = chaos. If you put one up in Townsville (400k north)
people totally lose even their limited ability to merge.
They sit there and try to work out what it means and each
person makes up their own rules. Frustrating.
Personally I take a few risks with traffic design and derive
solutions that aren't in any of the manuals (similar to
Monderman's approach) many of which are intuitive (which
Monderman's are, they are not counter intuitive, our current
design practice is). If it all goes pear shaped and I wind
up in front of the coroner (again) then I rely on the fact
that it was my professional judgement. If that is questioned
or he/she makes an adverse ruling so be it. I just like
things that work even if I can't totally explain why or show
it too you in a manual.
And for those who deal with Meyers-Briggs - god it is funny
watching the ISTJ's trying to figure out what I'm up to or
why some things actually work.
Cheers
BrettM