Adapting to Road Conditions
The spread of adaptive cruise control may bring an unexpected bonus
Sitting in stationary traffic is, at best, a Zen experience. Drivers mired in a jam lcam 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 arc 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 Kemer, a researcher for Daimler Chrysler, 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 100 km an hour). Dr. Kemer 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.
Stationary traffic can drive people mad. However, according to American and German researchers, adaptive cruise control (ACC) can help drivers ACC adapts a car's to keep a safe distance from the one ahead by using to monitor the road ahead. ACC is safer than manual driving because it significantly reduces the and collisions and congestion in addition. According to Dr. Davis' computer model, if of cars use ACC, can be improved significantly. However, ACC should not be seen as a . In conditions, it may even cause extra jams, according to a computer model. But this situation can be improved by reducing in ACC-equipped vehicles.
AI explanationShows the answer. Tap to open.
Question Focus: Synonym match - summary says 'help drivers' and passage says 'take back control'
Correct Answer: take back control
Why this is correct: The passage clearly says drivers can take back control over the roads by using ACC. The summary paraphrases this idea as ACC helping drivers, so we must copy the exact phrase from the passage.
Passage Reference: 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
Common Mistake: Students may write relax or reduce stress because of the opening paragraph, but those ideas are not stated as solutions. This is a paraphrase trap.
Paraphrasing: Passage: 'take back control over the roads' = Summary: 'help drivers [do something]'
Tips: When the summary says 'help drivers', look for a verb phrase in the passage that explains how.
Key Vocabulary:
- cede = give up
- mired = stuck
Question Focus: Direct detail match
Correct Answer: speed
Passage Reference: 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.
Why this is correct: The passage says ACC automatically adjusts the vehicle's speed to keep a safe distance. The summary uses 'adapts a car's', so the missing noun is speed.
Common Mistake: Some students write distance, but ACC adjusts speed to control distance. This is a causation trap.
Paraphrasing: Passage: 'adjusting that vehicle's speed' = Summary: 'adapts a car's [noun]'
Tips: Check what is directly controlled by the system, not the final result.
Key Vocabulary:
- adjust = change
- maintain = keep
Question Focus: Direct factual detail
Correct Answer: radar
Passage Reference: It employs radar to monitor the road ahead of a vehicle
Why this is correct: The passage clearly states that ACC employs radar to monitor the road ahead. The summary repeats this idea almost exactly.
Common Mistake: Students sometimes write technology or sensors, but these are not the exact words in the passage. This is a synonym trap.
Paraphrasing: Passage: 'employs radar to monitor' = Summary: 'using [word] to monitor'
Tips: When the wording is the same, copy the exact technical word from the passage.
Key Vocabulary:
- monitor = watch
- employ = use
Question Focus: Cause explanation - safety benefit
Correct Answer: system's reaction time
Passage Reference: 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.
Why this is correct: The passage explains ACC is safer because it reduces the system's reaction time. The summary shortens this idea but keeps the same meaning.
Common Mistake: Writing reaction time only loses the owner 'system's'. Missing words can change meaning. This is a partial truth trap.
Paraphrasing: Passage: 'reduces the system's reaction time' = Summary: 'reduces the [noun phrase]'
Tips: Be careful with possessives like 'system's' - they count as one word.
Key Vocabulary:
- forestal = prevent
- shunt = crash
Question Focus: Specific data figure
Correct Answer: 13%
Passage Reference: 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.
Why this is correct: Dr. Davis reports that 13% of cars using ACC can already improve traffic flow. The summary refers to this exact percentage.
Common Mistake: Many students choose 20%, which appears earlier but refers to completely preventing jams. This is a wrong section trap.
Paraphrasing: Passage: 'as low as 13%' = Summary: 'if [number] of cars use ACC'
Tips: Always check which statistic matches the exact result described.
Key Vocabulary:
- significantly = a lot
- rate = percentage
Question Focus: Result of ACC usage
Correct Answer: flow of traffic
Passage Reference: even a rate of use of ACC as low as 13% can improve the flow of traffic significantly.
Why this is correct: The passage says ACC can improve the flow of traffic significantly. The summary repeats this result.
Common Mistake: Students may write congestion, but congestion is the problem, not what improves. This is a reverse meaning trap.
Paraphrasing: Passage: 'improve the flow of traffic' = Summary: '[something] can be improved'
Tips: Check whether the gap needs the problem or the positive outcome.
Key Vocabulary:
- flow = movement
- congestion = traffic jam
Question Focus: Author's limitation statement
Correct Answer: panacea
Passage Reference: ACC is not a panacea. Dr. Davis got less promising results for more complex road conditions, particularly those near junctions.
Why this is correct: The passage clearly states ACC is not a panacea, meaning it is not a perfect solution. The summary directly reflects this warning.
Common Mistake: Some students write solution, which changes the meaning and is not from the passage. This is a synonym trap.
Paraphrasing: Passage: 'not a panacea' = Summary: 'should not be seen as a [noun]'
Tips: Unusual words like this are often copied directly from the passage.
Key Vocabulary:
- panacea = cure for everything
- junction = crossing
Question Focus: Problem conditions for ACC
Correct Answer: complex road
Passage Reference: Dr. Davis got less promising results for more complex road conditions, particularly those near junctions. And a similar model built by Boris Kemer, a researcher for Daimler Chrysler, in Stuttgart, Germany, indicates that in certain bottleneck conditions, ACC may even cause extra congestion.
Why this is correct: The passage mentions more complex road conditions and also bottleneck conditions where ACC performs poorly. Both are accepted answers because both appear in the text.
Common Mistake: Writing junctions alone is too narrow and misses the general category. This is a partial truth trap.
Paraphrasing: Passage: 'more complex road conditions' = Summary: 'In [type of] conditions'
Tips: When two phrases describe the same problem area, both may be accepted.
Key Vocabulary:
- bottleneck = narrow point
- ameliorated = improved
Question Focus: Method to improve ACC performance
Correct Answer: headway
Passage Reference: 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.
Why this is correct: The passage explains that reducing headway can improve traffic flow with ACC. The summary paraphrases 'shortening' as 'reducing'.
Common Mistake: Students may write distance, but the passage uses the technical term headway. This is a synonym trap.
Paraphrasing: Passage: 'shortening the headway' = Summary: 'reducing [noun]'
Tips: Always use the technical term given in the passage, not your own word.
Key Vocabulary:
- headway = time gap
- simulation = computer model
General Tips:
- Summary completion questions follow passage order. Use the previous gap to find the next answer faster.
- Always copy the exact word or phrase from the passage. Synonyms are usually wrong.
- Check grammar clues around the gap like articles, prepositions, and verbs.
- Be very careful with numbers and percentages. Different figures often describe different results.
- Keep an eye on the word limit. Extra words automatically lose marks.
The rest of this explanation is for members. Sign in free to read why the other options are wrong, key words and tips.
Sign in to read the full explanation