EigoPro 準1級読解 — The Science of Traffic Jams

Anyone who has crawled through a tailback on an open motorway knows the peculiar frustration of a traffic jam with no apparent cause: no accident, no roadworks, no bottleneck—just an inexplicable wall of brake lights that eventually dissolves as mysteriously as it formed. Physicists call this a "phantom jam," and for decades it puzzled engineers who assumed that congestion must always trace back to a tangible obstruction. The truth, it turns out, is stranger and more instructive: a jam can emerge from nothing more than the collective behaviour of ordinary drivers. The mechanism is a cascade. When traffic density passes a critical threshold, the system becomes unstable. A single driver tapping the brakes—perhaps glancing at a phone, perhaps merely drifting too close to the car ahead—forces the driver behind to brake a little harder, and the one behind that harder still. This amplification travels backwards through the stream of cars as a compression wave, much as a sound wave propagates through air. Crucially, the wave moves upstream even as the cars themselves continue forward, which is why a jam can sit in a fixed stretch of road while drivers pour into the back of it and trickle out of the front. What makes the phenomenon so revealing is that no individual is at fault, yet everyone suffers. Each driver responds rationally to the car in front, but the aggregate of those rational responses produces a collectively irrational outcome. This is the signature of a complex system, in which simple local rules generate large-scale patterns that no participant intends or controls. Recognising this has practical consequences. Engineers have found that smoothing the flow—through variable speed limits, ramp metering, or, increasingly, the steady pace of automated vehicles—can suppress the instability before it cascades. The lesson extends well beyond the motorway: wherever many agents interact under congestion, from financial markets to crowded corridors, order and chaos may be separated by nothing more than a gentle tap on the brakes.

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この単元の問題を3問、解説つきで公開しています

準1級 · 読解 · 全5問

問 1

What is the main idea of the passage?

Individual drivers who glance at their phones are chiefly to blame for serious traffic congestion.
Automated vehicles are the only reliable way to eliminate congestion on motorways.
Traffic jams are almost always caused by accidents, roadworks, or other visible obstructions.
Traffic jams can arise spontaneously from the collective behaviour of drivers, revealing how complex systems work.

Phrase

a jam can emerge from nothing more than the collective behaviour of ordinary drivers

準1級読解科学ジャーナリズム主旨把握

⚡ひとことで

本文は「渋滞は明確な原因なしに運転者の集団行動から自然発生し、複雑系の仕組みを示す」が論旨。

選択肢の解説Choice Analysis

「Traffic jams can arise spontaneously from the collective behaviour of drivers, revealing how complex systems work.」

正解

第1段で原因のない『幻の渋滞 (phantom jam)』を提示し、第2段でその発生機構 (圧縮波の連鎖)、第3段で『単純な局所ルールが大規模なパターンを生む複雑系の典型』と一般化する。したがって「渋滞は運転者の集団行動から自然発生し、複雑系の働きを明らかにする」が主旨。

「Traffic jams are almost always caused by accidents」
= 渋滞はほぼ常に事故等の障害が原因 ━ 本文はまさにこの前提 (engineers assumed congestion must trace back to an obstruction) を覆す内容なので逆。
「Automated vehicles are the only reliable way」
= 自動運転車だけが唯一の解決策 ━ automated vehicles は緩和策の一例として挙げられるだけで『唯一』とは述べていない。
「Individual drivers who glance at their phones are chiefly to blame for serious traffic congestion.」
= 個々の運転者が主な責任 ━ 本文は『誰も悪くないのに全員が苦しむ (no individual is at fault, yet everyone suffers)』と明言しており正反対。

▦Collocation

パターン	意味	例
emerge from ~	~から生じる	A jam can emerge from collective behaviour.
trace back to ~	~に遡る	Congestion need not trace back to an obstruction.
collective behaviour	集団行動	the collective behaviour of drivers
an apparent cause	見かけ上の原因	a jam with no apparent cause
dissolve as ~ as it formed	形成時と同様に消える	It dissolves as mysteriously as it formed.

❝例文

The jam emerged from nothing more than ordinary driving.
その渋滞は普通の運転だけから生じた。
Engineers assumed congestion must trace back to an obstruction.
技術者は渋滞には必ず障害物の原因があると思い込んでいた。
The wall of brake lights dissolved as mysteriously as it formed.
ブレーキランプの壁は形成時と同じく謎めいて消えた。

💡Tip · 覚えるコツ

主旨設問は第1段の問題提起と最終段の一般化をつなぐ。本文は『原因のない渋滞 → 機構 → 複雑系一般』の三段構成。

問 2

According to the passage, why can a phantom jam stay in one stretch of road while traffic keeps moving forward?

The cars stop moving entirely until the wave has fully dissipated.
The drivers at the front deliberately slow down to hold the jam in place.
A hidden physical obstruction anchors the jam to that particular section.
The compression wave travels backwards through the cars even though the cars themselves keep advancing.

Phrase

the wave moves upstream even as the cars themselves continue forward

準1級読解科学ジャーナリズム詳細把握

⚡ひとことで

渋滞が一区間に留まるのは、圧縮波が後方へ進む一方で車は前進し続けるため。

選択肢の解説Choice Analysis

「The compression wave travels backwards through the cars even though the cars themselves keep advancing.」

正解

第2段で『この増幅は圧縮波として車列を後方へ伝わる』とし、続けて the wave moves upstream even as the cars themselves continue forward, which is why a jam can sit in a fixed stretch of road と説明する。波は上流 (後方) に移動するが車は前進するため、渋滞は固定区間に留まる。これを言い換えた選択肢が正解。

「The drivers at the very front deliberately slow down in order to hold the whole jam in place.」
= 先頭が意図的に減速 ━ 本文に意図的減速の記述はなく、原因は波の伝播という物理現象。
「A hidden physical obstruction anchors the jam」
= 隠れた障害物が渋滞を固定 ━ 本文は障害物なしで渋滞が起きる (phantom jam) と述べており逆。
「cars stop moving entirely」
= 車が完全に停止する ━ 本文は drivers pour into the back ... and trickle out of the front と車が出入りすると明言しており、完全停止ではない。

▦Collocation

パターン	意味	例
move upstream	上流(後方)へ移動する	The wave moves upstream.
continue forward	前進し続ける	even as the cars continue forward
sit in a fixed stretch of road	固定区間に居座る	A jam can sit in a fixed stretch.
pour into the back of ~	~の後方に流れ込む	Drivers pour into the back of it.
trickle out of ~	~から少しずつ抜ける	They trickle out of the front.

❝例文

The compression wave moves upstream against the flow of cars.
圧縮波は車の流れに逆らって後方へ進む。
A jam can sit in a fixed stretch while cars keep advancing.
車が前進し続けても渋滞は固定区間に居座りうる。
Drivers pour into the back and trickle out of the front.
運転者は後方から流れ込み、前方から少しずつ抜ける。

💡Tip · 覚えるコツ

detail 設問は本文の which is why (だから~) が答えの直結部。because/which is why の前にある事実関係を選択肢で言い換える。

問 3

What does the passage identify as the defining feature of a complex system?

A central authority coordinates the behaviour of every participant.
Large-scale order can only emerge when individuals behave irrationally.
Each participant deliberately works toward a shared collective goal.
Simple local rules produce large-scale patterns that no participant intends or controls.

Phrase

simple local rules generate large-scale patterns that no participant intends or controls

準1級読解科学ジャーナリズム詳細把握

⚡ひとことで

複雑系の特徴=単純な局所ルールが、誰も意図・制御しない大規模パターンを生むこと。

選択肢の解説Choice Analysis

「Simple local rules produce large-scale patterns that no participant intends or controls.」

正解

第3段で渋滞を the signature of a complex system と呼び、in which simple local rules generate large-scale patterns that no participant intends or controls と定義する。各運転者は前車に合理的に反応するが、その総和が集団としては不合理な結果を生む。これを言い換えた選択肢が正解。

「A central authority coordinates」
= 中央権力が調整する ━ 複雑系の核心は『中央の統制なし』に秩序が生じる点で正反対。
「deliberately works toward a shared collective goal」
= 共有目標に向け意図的に働く ━ 本文は no participant intends と明言しており、共有目標は否定される。
「Large-scale order can only ever emerge when individuals behave irrationally.」
= 個人が不合理に振る舞う時のみ生じる ━ 本文は each driver responds rationally と述べており、個人は合理的。集団結果のみ不合理。

▦Collocation

パターン	意味	例
the signature of ~	~の典型的特徴	the signature of a complex system
local rules	局所ルール	simple local rules
respond rationally to ~	~に合理的に反応する	Each driver responds rationally.
the aggregate of ~	~の総和	the aggregate of those responses
a collectively irrational outcome	集団として不合理な結果	produce a collectively irrational outcome

❝例文

Simple local rules can generate complex global patterns.
単純な局所ルールが複雑な全体パターンを生みうる。
Each agent acts rationally, yet the aggregate is irrational.
各主体は合理的に行動するが、総和は不合理になる。
No participant intends or controls the emergent pattern.
創発するパターンを意図・制御する参加者はいない。

💡Tip · 覚えるコツ

定義設問は in which / that 以下の関係節を本文から特定する。『rational な個人 vs irrational な集団』の対比が選択肢の引っかけ軸。

残り2問は、解いて確かめられます

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EigoPro 準1級 読解 — The Science of Traffic Jams

この単元の問題を3問、解説つきで公開しています

a jam can emerge from nothing more than the collective behaviour of ordinary drivers

the wave moves upstream even as the cars themselves continue forward

simple local rules generate large-scale patterns that no participant intends or controls

EigoPro 準1級読解 — The Science of Traffic Jams