Safe Speed Forums

The campaign for genuine road safety
It is currently Tue Sep 29, 2020 06:27

All times are UTC [ DST ]




Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Mon Jul 05, 2004 00:52 
Offline
User

Joined: Sun Jun 20, 2004 05:18
Posts: 47
Location: New Zealand
Here's one of the most encouraging ideas I've seen for ages - using technology to improve speed and safety by reducing human reaction times:

http://www.economist.com/science/displayStory.cfm?story_id=2876941

Adapting to road conditions

Jul 1st 2004
From The Economist print edition


The spread of adaptive cruise control may bring an unexpected bonus




Adapt or die—of boredom

SITTING in stationary traffic is, at best, a Zen experience. Drivers mired in a jam learn to cede control to the powers that be, becoming at one with the universe as they breathe in the mind-numbing fumes all around. At worst, it is an ongoing battle for sanity. But now, according to several groups of researchers in America and Germany, there is something that drivers can do to take back control over the roads. Get adaptive cruise control. And, of course, use it.

Adaptive cruise control (ACC), as its name suggests, is a modified version of traditional cruise control. It employs radar to monitor the road ahead of a vehicle, automatically adjusting that vehicle's speed to maintain a safe distance from the one in front. This is safer than manual driving because it reduces the system's reaction time from nearly a second (human) to practically instantaneous (machine), thus helping to forestall shunts. But ACC may have a useful side-effect, arising from the fact that another effect of slow human reaction times is to produce traffic jams on apparently open roads.

Such jams start when a car slows suddenly to allow, for example, another vehicle to enter the traffic stream. Slow reaction times mean that instead of responding smoothly, the drivers behind such a vehicle often end up slamming on the brakes. That slamming propagates backwards, and before long the traffic is at a standstill. So it makes sense that ACC would reduce not only collisions, but also congestion. What is unexpected is how few vehicles need to have it operating for all to benefit. As Craig Davis of the University of Michigan reports in Physical Review E, only 20% of cars need to employ ACC in order to prevent completely those jams that are caused by a slow lead car on a high-speed, single-lane road. According to Dr Davis's computer model, even a rate of use of ACC as low as 13% can improve the flow of traffic significantly.

ACC is not a panacea. Dr Davis got less promising results for more complex road conditions, particularly those near junctions. And a similar model built by Boris Kerner, a researcher for DaimlerChrysler, in Stuttgart, Germany, indicates that in certain bottleneck conditions, ACC may even cause extra congestion. These disappointing results can, however, be ameliorated by shortening the “headway” in ACC-equipped vehicles, according to Martin Treiber of the Dresden University of Technology, also in Germany.

Headway is the gap, measured in seconds, that a driver puts between himself and the car ahead. Since ACC reacts more quickly than a human, people who have it fitted can afford to allow less headway.

In his simulation, Dr Davis instructed both his ACC-equipped and his manually driven cars to leave about 1.1 seconds of headway (equivalent to 28 metres at about 100km an hour). Dr Kerner allowed for as much as 1.8 seconds, the distance at which drivers in Germany are taught to follow. But Dr Treiber says 0.9 seconds is safe and realistic. Using this headway in their simulations, he and his colleague Dirk Helbing saw big improvements in traffic flow even in the most dire road conditions. The question remains, of course, of whether real drivers will trust the technology sufficiently to allow it to follow the car in front so closely.

ACC has been an option in a number of luxury vehicles for several years. Now it is becoming available in mid-range cars. But its presence on the roads is still limited, and many people who have it do not use it. If drivers could be convinced to fit ACC and use it, it would not only improve their own driving experience, but also that of their fellow motorists

_________________
Alan Wilkinson (at http://www.fastandsafe.org)


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 09:35 
Offline
Member
Member

Joined: Thu Mar 11, 2004 00:24
Posts: 2400
Location: Kendal, Cumbria
I wouldn't feel safe following cars at a 0.9 second separation, even less so under the control of a computer!

This apparent gain in congestion under a simulated environment seems a bit suspect. Of course if you bunch all the cars up closer you increase the capacity of the road which reduces congestion, but I would seriously question the wisdom of doing so. Would this system take into account the fact that the car it is fitted to might be a "run of the mill" car with budget tyres, and the one it has just started tailgating at 0.9 seconds might be a sports car capable of stopping in a much shorter distance? I think not.

Also, what of the psychological effect of your car latching onto someone else's bumper in this way? Are they going to sit there happily and just assume "it's ok, he must have ACC"? What about the reduction in driver visibility that this tailgating causes?

This sounds like a case of someone setting up a simulation to prove what they want to prove.

_________________
CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 10:04 
Offline
Member
Member
User avatar

Joined: Sat Mar 20, 2004 09:59
Posts: 3544
Location: Shropshire
JT wrote:
This apparent gain in congestion under a simulated environment seems a bit suspect.


The fact that motorway traffic can be brought to a standstill by drivers having to brake with increasing severity as cars ahead slow down is well known. It was shown quite clearly on a TV program about congestion a few years ago, they had a camera mounted on a motorway bridge and you could see the ripple move back down the stream of traffic until it stopped just in front of the camera.

Researchers into traffic dynamics have apparently demonstrated that slowing the traffic flow down can, paradoxically, help to alleviate the problem. I guess that if everyone is going more slowly they don't have to react so violently to changes up ahead and the traffic keeps moving.

The problem is that when the 50mph signs illuminate on the motorway, everyone shoots past thinking "whats the problem, have they just been left on?" only to discover the reason right around the next bend - congestion.

However, as JT says, I would hate the thought of being followed at 0.9 secs distance by a 1.3 Nova fitted with Barry's Bakelites - durable but not grip tyres at £5 a throw, ACC or no ACC!.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 12:27 
Offline
User

Joined: Sun Jun 20, 2004 05:18
Posts: 47
Location: New Zealand
Rigpig wrote:
However, as JT says, I would hate the thought of being followed at 0.9 secs distance by a 1.3 Nova fitted with Barry's Bakelites - durable but not grip tyres at £5 a throw, ACC or no ACC!.


Hang on there. Consider that the options are for ACC to start braking in 0.1 sec so you get 0.8 secs of free braking space compared with dear old Betty in the same car at 1.5 secs separation (if you are lucky) who takes 1.2 secs to notice something is happening and then has only half the free space for her Bakelites to slither over?

I do think there is a lot of room to use technology well and constructively to assist and augment human needs instead of it being commandeered by the bureaucracy to use destructively against motorists and against human nature.

_________________
Alan Wilkinson (at http://www.fastandsafe.org)


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 18:55 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
I don't believe there's much to be gained by having devices to 'help' driver reaction times - in fact, I believe that reliance on these devices will have quite the opposite effect.
The reason is, no matter how sophisticated a device is, it can only do anything once it detects something substantial in the path of the vehicle - it cannot detect things which, arguably, make up a large and often crucial part of driver reaction, eg. a ball bouncing into the road, party balloons tied to a gate, feet viewed underneath a parked vehicle, an emergency siren as you're approaching a green light, etc. etc. etc.
Properly observed and acted upon, these often give the driver a valuable extra few seconds to avoid an accident. A machine, on the other hand will often only react when it's too late.

Regards
Peter


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 21:15 
Offline
User

Joined: Sun Jun 20, 2004 05:18
Posts: 47
Location: New Zealand
Firstly, regarding safety, what you believe is unimportant. What actually happens is all that matters.

Secondly, regarding technological tools - they are there to assist and augment human skills, faculties and duties, not replace considered judgement.

Humans notoriously get tired, bored, distracted with monotonous chores like monitoring the car ahead. Machines do not. Use the machine for what it is good at and the human for what you are good at.

For example, humans react much faster to audible warning signals than visual ones. At the simplest level the machine could improve reaction times just by sounding an audible warning.

_________________
Alan Wilkinson (at http://www.fastandsafe.org)


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 22:49 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
alanw wrote:
Firstly, regarding safety, what you believe is unimportant. What actually happens is all that matters.


I believe that a reliance on such technological tools is not necessarily a good thing.

Quote:
Secondly, regarding technological tools - they are there to assist and augment human skills, faculties and duties, not replace considered judgement.


Yes, but it's a safe bet that they will replace considered judgement in many cases.

Quote:
Humans notoriously get tired, bored, distracted with monotonous chores like monitoring the car ahead. Machines do not. Use the machine for what it is good at and the human for what you are good at.


The car ahead isn't usually the problem. It's the car, truck or pedestrian suddenly crossing your path which is.

Quote:
For example, humans react much faster to audible warning signals than visual ones. At the simplest level the machine could improve reaction times just by sounding an audible warning.


A human can often judge when a pedestrian may be about to step off the pavement. A machine will only sound the alarm when the pedestrian is already in the path of the vehicle - by which time it could be too late.

Regards
Peter


Top
 Profile  
 
 Post subject:
PostPosted: Mon Jul 05, 2004 23:04 
Offline
User

Joined: Sun Jun 20, 2004 05:18
Posts: 47
Location: New Zealand
Pete317 wrote:
Quote:
Humans notoriously get tired, bored, distracted with monotonous chores like monitoring the car ahead. Machines do not. Use the machine for what it is good at and the human for what you are good at.


The car ahead isn't usually the problem. It's the car, truck or pedestrian suddenly crossing your path which is.



That depends entirely on where you mostly drive. I have a regular four hour commute to our major city so your assumption is quite untrue for me.

_________________
Alan Wilkinson (at http://www.fastandsafe.org)


Top
 Profile  
 
 Post subject:
PostPosted: Tue Jul 06, 2004 07:53 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
alanw wrote:
That depends entirely on where you mostly drive. I have a regular four hour commute to our major city so your assumption is quite untrue for me.


For you, yes. For me, sometimes. For millions of people who drive mainly in built-up areas, no.

Regards
Peter


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
[ Time : 0.329s | 13 Queries | GZIP : Off ]