How to build a speed detector?

[Jan Panteltje]

Or at least put in some hours of PROFESSIONAL driver training. An
instructor may be able to point out things that can be improved
(scanning rather than fixing on objects, maintaining awareness of
what's around you in case you have to avoid someone else and so on).
With experience and by developing good habits, almost anyone of normal
abilities can learn to drive safely.

Recently I was driving an old friend home, taking my time (maybe
35mph), going along the right-hand lane of a 4-lane non-
controlled-access road (Lakeshore Road) that has a lot of businesses
and other clutter along it. It was in the evening and traffic was
light. A guy in an SUV came up to the exit from a strip mall on the
right and didn't, as they often do (grrrr..), look like he wasn't
going to stop, then stop quickly at the exit, but kept going towards
my passenger door. Being aware (subconsciously, from scanning) that
there was nobody in the lane to my left, I hit the horn and swerved
(without braking) into that lane in a split-second and avoided a
collision. I looked back and the SUV had slid to a stop with its
bumper past the middle of the right lane (I'm not sure he ever saw me,
maybe just reacted to the horn). There's no thinking in such a
situation, it has to happen instinctively, sort of like a baseball
player- the plays and the moves have been practiced for real or in his
head so many times, that hopefully the right thing just "happens" when
the moment of truth comes. It also helps to have a car that listens
when you tell it to do something (a decent car in good condition), but
it's possible to drive defensively even in a crapbox.

Robert (Bob) Pease has written and self-published an inexpensive ~500
page book on driving- aimed at new drivers, which Amazon.com carries.
ISBN: 0965564819 I've never read it, but it's written by an
electronics guy and is probably helpful (reviews are a bit "mixed").
;-)

Best regards,
Spehro Pefhany

Yep, that is the way it works, when our (thank God no longer) female minister
of traffic Mai Weggen was still at it, I was on the way from work to home,
narrow road, 2 lanes, no separation, the one that has all the car wrecks on
the side in winter... And normal situation., almost bumper to bumper,
from 2 sides, at 80km/h, and here comes politica, in big black monster,
passing car after car it seemed (and you CAN'T there), from the opposite side.
I saw the black monster coming into my lane and LUCKY there was small paved
area on the side, I swung into it, the black monster passed within a hairs width,
and I swung out of that area back in the road.
Later she had a whole lot of problems about that, must have pissed some other ones
too, I would have locked her up.
It seems she instructed the driver to ignore all traffic rules and he did (
executive order), because she was late for a meeting.
Later I think she went to Euro parliament, not sure if she is still there.
At least that is in Belgium and far away ;-)
JP

 

[Julie]

Hi Julie.

According to whom? I was awake in drivers ed when the told us that 2
sec was a safe distance. That included 55 mph. Your rule would put
the distance at 5.5 sec which I know is a big space and as others
have mentioned, it's only going to leave a gaping hole for someone
to fill. Then you'd have to slow down to get your safe following
distance back.

I made a mistake. I now recall (correctly) that what I was taught was 1 car
length for each 10 mph ...

Regardless, I did a little research, and there doesn't seem to be any consensus
on the topic at all. From what I saw, there was about an equal number of
proponents for a '3 second' rule as opposed to 2 seconds.

Regardless of the # of seconds, that all seems to assume that the person
braking in front of you stops in approximately the same distance as you, and
not sooner. If they stop sooner (as in hitting the end of a series of already
stopped cars), 2 or 3 seconds won't really matter -- you are going to hit them
unless you can defensively navigate around them.

Regardless, any 'rule' doesn't work unless there is cooperation among drivers
for the exact reason that you point out of (inconsiderate) drivers merging into
your safety gap.

 

[Julie]

First accident: ....
Second accident:

....

No offense, but you should *REALLY* consider some professional driver training
and defensive driving classes... A speed detector isn't going to help you in
the situations that you describe...

 

[Activ8]

I made a mistake. I now recall (correctly) that what I was taught was 1 car
length for each 10 mph ...

My drivers ed teacher started out quoting an absolute footage for a
given speed or speeds IIRC - from the MVA handbook, He gave the 2
second rule so that we could have something prctical. Figure it
wouldn't be easy to take us out to learn to estimate distances.

Regardless, I did a little research, and there doesn't seem to be any consensus
on the topic at all. From what I saw, there was about an equal number of
proponents for a '3 second' rule as opposed to 2 seconds.

That figures. The figure probably varies in the drivers handbooks
from state to state as well as the opinions of others.

Regardless of the # of seconds, that all seems to assume that the person
braking in front of you stops in approximately the same distance as you, and
not sooner. If they stop sooner (as in hitting the end of a series of already
stopped cars), 2 or 3 seconds won't really matter -- you are going to hit them
unless you can defensively navigate around them.

YEs. Thanks for reminding me of Fred's "0 mph tree, which don't like
to move for anything" statement which is still good for a chuckle.

Regardless, any 'rule' doesn't work unless there is cooperation among drivers
for the exact reason that you point out of (inconsiderate) drivers merging into
your safety gap.

Thus my desire for a monster truck Gotta go before I start
ranting

 

[Activ8]

I have been getting a lots of reply here.
Maybe I should tell out the whole story.

First accident:
One fine day while driving on the highway at 110 KM/H, it rained suddenly.
(wasnt really suddently, it was already raining at that area some time ago).
I was on the most-right lane on a four lane highway. (its Malaysia,
remember)
I need to make an exit on the left. As I slowly make my way to the left
lane, one super slow MPV was about a hundred meters away. It takes me some
time before I really know that the car is moving at a slow pace, due to poor
visibility and slow judgement. I hit the brake, but it wouldnt slow down. My
car is basically floating already. I try to steer left to avoid collision.
It doesnt work as well. When I finally able to turn, it was already too
late.
Forget about four second rule here. Forget about speed limit here. My
fault - poor judgement and i should have slow down.

One fine day while wide awake in drivers ed, I assimilated the
knowledge that when it starts raining, the road becomes very slick
because the oils leaked from the POSs of others floats on the thin
layer of recently deposited H2O. Then I assimilated more knowledge
about hydroplaning, skidding, pulling out of skids, and just plain
slowing down.

Second accident:
Another fine day, this time happends on Sunday. I was driving at about 60
KM/H. Approaching the traffic light behind a car. Suddenly a taxi from the
left side dash out (ignoring the red traffic light). The car in front of me
make an emergency brake. I, way over 2 seconds behind the car did my best to
stop the car. It takes me much too long to figure out that the car is
slowing to zero. (He can still make it, the taxi driver has make his timing
perfectly to avoid accident.) Lucky enough there car behind of me is way too
far away. Else there could have been another chain accident. (very common in
Malaysia).

One other fine day, I got friggin' tired of slowing down and started
taking evasive action like passing on the right shoulder, using
sidewalks free of pedestrians, etc. I've had much success and
haven't blown a tire, killed a balljoint, or bent anything up too
badly, yet.

Third accident:
This has nothing to do with me. I used the wrong word at the first place.
(should be my car not me) I was sleeping actually when the accident happens.
My brother crashed my car. (This is the worst of all - till now my car is
still in the workshop.) Lucky enough no injury to him nor anyone is hit. He
slammed against the road divider.

Sounds like a bad day like the day I decided to never (almost) ever
let anyone drive my car.

I reall need some kind of speed detector.
The one that I saw on the internet is Origin b2.
http://www.pollmatrix.com/originb2.htm
Price is £429.95. (enough to pay for a Volvo s40 - downpayment)

You'll be safer in a Volvo. "Son, take my Volvo."

 

[Julie]

Thus my desire for a monster truck Gotta go before I start
ranting

My boyfriend currently has a large truck (lifted Ford diesel). Some years
before that, he had a Fiero. He says that he got a lot more 'respect' in the
Fiero than from the truck -- it seems that whenever someone sees a large truck,
they think that they "don't want to get stuck behind that slow thing" and pull
out in front of him all the time... So, if you go the big truck route, get a
thrasher or something w/ a big plate-metal front bumper.

 

[Rene Tschaggelar]

My boyfriend currently has a large truck (lifted Ford diesel). Some years
before that, he had a Fiero. He says that he got a lot more 'respect' in the
Fiero than from the truck -- it seems that whenever someone sees a large truck,
they think that they "don't want to get stuck behind that slow thing" and pull
out in front of him all the time... So, if you go the big truck route, get a
thrasher or something w/ a big plate-metal front bumper.

I'd rather get nervous when I have a big truck behind me. The reason
being : When I have have to break quickly there is a chance in having
the trunk in the back, since it takes longer for the truck to break.
Sure, the truck would be liable but that isn't really going to cheer
you up when you're flattened.
Behind a truck, you're much safer, as your brakes are much faster that
the truck's.

Rene

 

[YD]

I had involved in car accident for three times in the past two months.
I realise that I would be good if I have a device to read the distance and
the speed of the car in front of me, of course this device must be able to
function in the rain. I have seen this devices in the internet, but the cost
if way too costly. Any help? Thank you.

Regards,
Desperate

Put your wife in the passenger seat, she'll scream her head off
whenever you close in on something. I know, fairly bulky and high
maintenance, not electronic, but as you already have her at hand there
won't be any added expense.

On a serious note, get a checkup, something seems to be wrong with
your eyesight or general health, slowing your reaction time.

- YD.

 

[YD]

Nowadays they're saying you should keep a 4 second following distance at
any speed.

-Michael

Around here they seem to think the only safe speed is 0. Statistically
it makes sense, an immobile object is pretty unlikely to suffer an
accident.

- YD.

 

[Ian Stirling]

This is *minimum* following distance, based on reaction time only.
It assumes that the driver has normal reflexes and eyesight,
is not distracted, and that he will be braking at a rate
at least as great as the guy ahead who just jammed on his brakes.

Not quite.
Let's take two cars going 35m/s (about 70mph) spaced 4s apart (140m).
One slams on the brakes, and begins to decellerate at 10m/s^2 (he's got
good brakes and it's a dry road)
Now what happens.
Let's say that the driver following takes a second to react.
So, now the car in front is traveling at 25m/s and distance between them
has dropped to 135m.
The back car brakes at 0.5G (poor tyres and brakes).
It'll take s=ut + 1/2 a t^2
meters to stop, or as we know t (35m/s /5m/s^2 = 7s)
s = 35m/s*7s + 0.5*-5m/s^2 * 7^2
s = 245 -122 = 123m.

The other car takes a further 31m to stop, so is 166m away from where the
first car started braking, leaving a gap of 43m.

For the second car to actually hit the first car at speed, it needs to
actually run into something fairly solid and the second driver not
to be able to brake very effectively.
Just jamming on anti-lock brakes, even with good tyres won't do it.

 

[Rich Grise]

Regardless, any 'rule' doesn't work unless there is cooperation among drivers
for the exact reason that you point out of (inconsiderate) drivers merging into
your safety gap.

THen you back off and make a safety gap for the next beavis to pull into,
back
off again for the next beavis, and so on. You'll still get there, and much
more likely in one piece, with less heartburn.

But everybody's in such a hurry these days - I guess they don't realize that
no matter where you go, or how fast you get there, It's still you that's
there when you get there.

Cheers!
Rich

 

[Rich Grise]

I had an MR2 some years ago, and had a number of accidents and near
accidents
with it, all where I was suddenly faced with a slow-moving car right in
front
of me. I couldn't figure it out, I had a great driving record before
that car.
Was I having too much fun driving a neat car?
Yes.


Well, after totalling it out (got a nice settlement from the insurance,
at least)
and going back to a good driving record, it slowly dawned on me what had
been happenning. Other people just didn't SEE that car! I don't know if it
was the color (kind of a darker silver) or the low profile, but people were
pulling out of side streets and driveways, RIGHT in front of me.

Depending on other people seeing you, or doing anything sane at all, is
absolutely the stupidest driving decision you can possibly make, except
maybe driving blindfolded.

In other words, pay fucking attention to what you're doing.

Feh.
Rich

 

[Rich Grise]

Right, and if it were painted silver, they would be rear-ended a lot more
often.

All things being equal, a silver colored vehicle is a lot more difficult to
discern than most other colors.

Right. I have a Fiero, and it's essentially the color of dirt, i.e.
invisible.
So I drive with my lights on.

And I look in front of the car, and I don't assume that the idiot in the
other
car is going to do _anything_ predictable, except probably follow Newton's
laws for small intervals, until he makes a stupid move. When I drive my car,
I'm on red alert.

I totaled a car last 4th of July: I ran a red light and T-boned some guy.
Not a lot of damage, no injuries, and everybody was insured. I was on my
way to my PHB's house to spend the day staring at him and his relatives.
The car was a piece of crap that some guy had swindled me into buying.

So, in one fell swoop, I got out of spending the day at the PHB's house,
and got rid of a piece of crap car that I couldn't have sold for what I
owed on it. The insurance company paid me and the guy I owed, and let me
keep the wreck, which still drove. It was just ugly. So I was negligent,
but it doesn't have to have been buried very deeply in my subconscious
to have been deliberate.

But my point is, there's only one person ultimately responsible for your
safety, and that's you. Shirking that, which seems rampant these days,
and not just re driving, is probably one of the biggest causes of
problems that we have these days.

Oh, Well.
Rich

 

[Rich Grise]

I'm aware of the US americans to be absolutely insane on this aspect.
I myself drove in LA at 65 mph with 5m distance, some factor 10 below
the 2 seconds. The uneasy feeling was terrible. You had to concentrate
during every heartbeat. No looking around, no thinking ahead. No
day-dreaming.

I'll stick with our 2 seconds.

Well, a moving automobile is not a fscking Jacuzzi, for Christ's sake.

Good Luck!
Rich

 

[Rich Grise]

I one had a bus (local line) full of people at 80km/h (max speed) 1 meter
behind me for a long time.
That really pissed me off, so I put on the emergency lights, and forced
him to stop.
I stepped out of the car, wanting to 'give it to him', he got the message
and somehow turned around...
I think those tailgaters are idiots.
They are not real commies, maybe Steve can shoot a few ;-)

I'd like to have some James Bond device, like spikes or an oil slick,
except that'd get the guy behind the tailgater. Maybe a bumper sticker
that says, "Danger! Tailgaters will be Spiked!" with a little picture
of one of those tetra-whatever things - 4 points at the vertices of a
tetrahedron. Maybe a couple of baskets that can be dumped, with a
bunch of those things in them, so the tailgater knows you're serious.

And a big mirror for when they're tailgating at night.

Cheers!
Rich

 

[Rich Grise]

That's just dumb- the damned engine is not going to last any amount of
mileage driving at those high speeds. I will never push mine above 3000
RPM-

There's something wrong with your car. Mine loafs along at about 1500 at
around 65 MPH.

Good Luck!
Rich

 

[Rich Grise]

I like driving to be an adventure and I certainly not of sub-normal
IQ. If I want to drive fast I will. I won't endanger other road users
while doing so though. It's perfectly possible to drive fast and be
safe, you just have to pick *where* you drive fast. Busy roads in
rainstorms are not the place and SUVs are not the tool.

I guess you'd be upset if I passed you with a clear lane between us on
a dry, empty, straight road if you were doing 65mph and I was doing
120.

Not me. It's clear that you at least look in front of your car. ;-)

Cheers!
Rich

 

[Rich Grise]

It's pretty amazing.
I try to drive at a constant speed and let the distance to the next
car change as the traffic ahead does the stop/go/accordian thing.
The guy behind just can't stand going at a constant speed and feels
compelled to pass me, usually with a hand gesture, so he too can do the
accordian thing. I think cars must have a secret brainwave killer;
probably put in there by people who make brake linings.
mike

I wonder what blimp rides cost? I'd like to do some aerial movies of
some experiments I've done while driving, to see if my impressions
are accurate on a larger scale - i.e., do some of these things
while observing traffic flow from aloft. I think a large enough
number of cars could be considered to follow some kind of flow
mechanics - there are probably formulas.

Anyway, one thing I've noticed is that when the road loses a
lane, there's always a jam-up as people jockey for position
to be next through the gate. And there's always the smart-
asses who drive past a whole line of cars, and then get
into ego duels with the people who don't want to let him
in - I've found that letting cars in actually smooths the
flow for everybody. It like smooths out the discontinuity.
I'd also like to look at shock waves. There could be some
innocuous distraction, and somebody slows down to look
at it. The next guy slows down because he sees brake
lights. Then there's sort of a chain reaction, as more
and more people start seeing brake lights, and wondering,
"WTF?" Then there's a clump. But then the ones in front
get going again, and the clump spreads out, but by that
time, the ass end of the clump is building from new
arrivals. Even long after the original distraction is
gone.

If I won the lottery, I'd like to do that experiment.

Cheers!
Rich

 

[Rich Grise]

I have been getting a lots of reply here.
Maybe I should tell out the whole story.

First accident:
One fine day while driving on the highway at 110 KM/H, it rained suddenly.
(wasnt really suddently, it was already raining at that area some time ago).
I was on the most-right lane on a four lane highway. (its Malaysia,
remember)
I need to make an exit on the left. As I slowly make my way to the left
lane, one super slow MPV was about a hundred meters away. It takes me some
time before I really know that the car is moving at a slow pace, due to poor
visibility and slow judgement.

-----------------^^^^^^^^^^^^^^

Yes, Negligence.

I hit the brake, but it wouldnt slow down. My
car is basically floating already.

You were _already hydroplaning_, yet took no measures to get the wheels
back on the road? That's double stupid.

I reall need some kind of speed detector.

You reall[sic] need to throw your brain into gear for a change.

Clue up.
Rich

 

[Ian Stirling]

Depending on other people seeing you, or doing anything sane at all, is
absolutely the stupidest driving decision you can possibly make, except
maybe driving blindfolded.

Most people are not actually out to cause you harm.
It may just seem that way.
Driving defensively fundamentally includes making yourself known
to other road users.

In other words, pay fucking attention to what you're doing.

Which includes not picking low visibility cars, and making sure your
running lights/brake lights/horn are in working order.