近年，ラウンドアバウトは，安全性の向上や停止時間短縮による環境負荷低減が期待できる平面交差構造として欧米諸国等で積極的に導入されている．我が国でも導入に向けて研究が行われてきているが，積雪地域特有の課題については十分に検討されていない．そこで，苫小牧寒地試験道路に模擬設置したラウンドアバウトにおいて，秋期と冬期に被験者を用いた走行実験を行い，路面状態の違いによる運転挙動の変化や主観評価への影響に着目し分析を行った．その結果，雪氷路面時は乾燥路面時と比べて，車両の環道流入時の速度が低下し，走行位置が中央島に近くなる傾向を確認した．また，冬期は，走りやすさや安心感の評価が低くなった．雪氷路面時に区画線位置が不明確になることが一因と考えられ，走行位置を明確にする対策が必要であることが分かった．

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概要. ラウンドアバウトの環道を有限個のセルに分割し，各セルに車両が存在する確率の時間発展を記述する差分方程式が導かれている．その方程式の定常解は，ある緩やかな条件の下で安定であることが示される． さらに，流入規則にしたがって運用されているラウンドアバウトは，環道上の車両存在確率が高いときに車両割込み違反の影響を受けやすいことが示される．

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ラウンドアバウトの導入検討に際しては，流入部の交通容量の確認が重要となるが，我が国では未だその事例が少なく，ラウンドアバウトの幾何構造が交通容量に与える影響が十分明らかになっていない．また，ラウンドアバウトの流入交通容量は，我が国ではギャップアクセプタンス確率に基づく推定式により算定することとしているが，その際に必要となる車頭時間パラメータに幾何構造諸元が与える影響も明らかになっていない．そこで本研究では，我が国のラウンドアバウトで得られた観測データを用いて，幾何構造諸元が流入交通容量に与える影響を分析し，幾何構造諸元と交通条件を説明変数とする車頭時間パラメータの推定式を提案した．そして，これに基づきラウンドアバウトの幾何構造諸元が流入交通容量に与える影響を定量的に明らかにした

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 1. Introduction

 In facilities hosting large crowds, such as railway stations, stadiums, and convention centers, visitors in transit have different destinations. Pedestrian flows are therefore complex, unlike single-direction building evacuations. When multiple flows cross, they can easily become stacked because of the sudden increase in density and the difficulty in avoiding other people coming from different directions. Moreover, walking in a disordered crowd is mentally stressful, and even poses the risk of colliding with others. Solving such congestion is essential for flow efficiency, safety, and user comfort.

 This paper proposes a new flow-control system called a Pedestrian-Roundabout, and reports on its effects through the results of two sequential full-scale experiments.

 

 2. Pedestrian-Roundabout Proposal

 The Pedestrian-Roundabout is an architectural device developed by the authors to optimize the complex pedestrian flows at intersections. In a Pedestrian-Roundabout, a large obstacle several meters in diameter is placed at the center of a pedestrian intersection and, similar to how an automobile roundabout works, pedestrians are required to walk in one direction around it.

 

 3. Methodology

 To determine the effects of placing such an obstacle on the crowd flow characteristics and detailed walking behavior at the crossing point, we performed two full-scale laboratory experiments: one in 2018 with 48 participants, and another in 2019 with 96 participants. The shape of the obstacle, pedestrian density, and walking direction constraint were all varied in the experimental conditions to determine the effective factors for traffic flow optimization. A short questionnaire evaluating the psychological quality of the walk was also conducted after each trial.

 A very accurate pedestrian trajectory data associated with each pedestrian's ID was obtained using two-dimensional barcode markers and the authors' original image processing programs. Based on these IDs, each trajectory was connected to the other participants' information, including their psychological walk evaluation.

 

 4. Results

 Diagrams in Fig. 8 indicate the walking trajectories in some representative cases with an emphasis on walking speed reduction. When four flows crossed in a normal right intersection (Fig. 8 4X-FR-VO), the center part became highly congested with pedestrians walking in different directions (Fig. 9). In such a complex crossing situation, pedestrians needed to perform avoidance behavior, namely, speed reduction and detouring, quite often. According to the questionnaire results, the participants perceived the walk as more difficult when they necessitated stronger avoidance.

 By just placing a cylinder shape obstacle with a 4 m diameter in the center of this intersection (Fig. 8 4X-FR-CI), it was observed that the speed reduction was restrained. Furthermore, constraining the walking direction to one-direction (Fig. 8 4X-RA-CI) reinforces this effect, and the trajectories became smoother due to the less detouring around others. The results indicated also that the 4 m diameter obstacle worked more efficiently than a smaller size 2 m obstacle. When the obstacle had edges in the plane, the flow stacked nearby the corners (Fig. 8 4X-FR-SQ₀, 4X-FR-DI₀, 4X-FR-DI₃₀).

 

 5. Conclusions

 According to the results of our experiments, placing a large obstacle at the center of a complex intersection and letting pedestrians detour around it have positive effects on streamlining the flows. Thus, by introducing the Pedestrian-Roundabout, a reduction in the congestion and a walking difficulty improvement can be expected.

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本研究では，交差点構造の異なる複数のラウンドアバウトにおいて，外部観測調査を行い，利用者挙動データを取得，分析することで，歩行者と車両に関連する潜在的な危険性について明らかにし，ラウンドアバウトにおける歩行者安全性に資する構造改良案について検討した．その結果，停止線と横断歩道間の距離が歩行者の首振り安全確認の実施，歩行者と車両の潜在的な交錯危険性に影響を及ぼすことがわかり，停止線と横断歩道間の距離を1m以内にすることで危険な挙動が減少し，最大でも3m程度の長さに留めておくことが望ましいことがわかった．また，流入出車両の速度推計モデルより，流入車両については環道に対して直角に近く流入部を取り付けること，流出車両については環道と横断歩道間の距離を短くすることが速度抑制対策に繋がることがわかった．

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近年，訪日外国人レンタカー利用者の増加に伴い，訪日外国人レンタカー利用者の事故件数が増加している．本研究では，訪日外国人レンタカー利用者の事故特性を把握するために，利用可能な事故統計を用い，日本人および日本の免許証を有する外国人とそれ以外の免許を有する外国人の交通事故の項目別の構成比を統計的に比較した．その結果，日本人と比較した際に訪日外国人レンタカー利用者に共通する事故の特徴，および近年，急激に増加している韓国人，台湾人，香港人レンタカー利用者の事故の特性を明らかにした．

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本研究では，名古屋市中区に位置する交差点で実施されたラウンドアバウト（RAB）試行運用について，各種調査に基づき，試行運用中の自動車利用者の意識変化や交通課題について分析した．インタビュー調査より，RAB 流出時ウインカー点灯の通行ルールの認知度が高くない状況であるとわかった．テキストマイニング分析より，自動車の減速に関する因子が交差点に対して好印象，交差点の通行ルールや戸惑い，不安感の因子が悪印象と，利用者の慣れやルール認知度が印象と関連することがわかった．外部観測や実走調査より，流出時のウインカー点灯割合が，試行運用開始から3 ヶ月後でも利用者の約3 割と低い状況であり，また，自動車の環道内通行位置については6 割以上の車両がエプロン上を通行しているなど，運用や構造上の改善余地があることを示した．

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ラウンドアバウトは，一般の交差点に比べ，安全性，円滑性，経済性に優れ，各国で積極的に導入されている．日本においても，現在，指針等の整備が進められているほか，試験道路における実証データも収集されつつある．しかし，日本国内でのラウンドアバウトの導入事例は少なく，特に，日本の北部地方は積雪寒冷で気象条件が厳しいことから，冬期間におけるラウンドアバウトの効率的な維持管理手法の確立が必要である．
このことから，本研究では積雪寒冷地におけるラウンドアバウトの問題に特化し，冬期の安全な道路交通機能の確保に資することを目的に，模擬ラウンドアバウトにおいて各種試験を行い，ラウンドアバウトの効率的な除雪工法について検討した．その結果，除雪機械の選定手法及び視認性を考慮した堆雪位置及び高さの提案が可能となった．

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近年，我が国では，地域の自発的な取り組みによりラウンドアバウトの社会実験や導入事例が増え，平成25年6月には道路交通法の一部を改正する法律が成立し，ラウンドアバウトが環状交差点として法的に位置付けられた．一方，未だラウンドアバウトの導入事例が少ないため，ラウンドアバウトを導入する際に必要となる，自動車や横断歩行者・自転車の交通状況の実測値を踏まえた交通容量上の判断基準は明確になっていないのが現状である．本研究では，ラウンドアバウト運用のされている既存円形交差点やラウンドアバウト社会実験での観測データを用いて，実現交通量の特性を分析した上で，軽井沢町六本辻ラウンドアバウトで観測された交通容量に関する考察を行うとともに，提案されている横断歩行者等を考慮した流入部交通容量推定式との比較を行う．

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Traffic priority at roundabout entries has played an important role in the history of roundabouts. When roundabouts were proposed and implemented at the beginning of the 20th century, the importance of the priority rule was not well recognized and the nearside priority rule was applied. However, the smaller traffic volume at that time did not reveal this problem until the increased traffic flow caused a locking-up problem at roundabouts. This was same in Japan where roundabouts were used before the World War II. After the World War 11, offside priority rule was proposed in some countries, and in 1958 this rule was tested on public roads in the U. K. In Japan, a traffic engineer proposed the offside priority rule in 1953, but this was ahnost neglected and roundabouts were removed. After the offside priority rule was made mandatory in the U. K. in 1966, the advantages of roundabouts were well recognized and this type of intersection was adopted in many countries including Australia, France, Germany and others. In this paper, the history of the priority rule at roundabout entries in Japan is reviewed in comparison with those of other countries.

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 Roundabout intersections began to be built in Western countries in recent years as a way to cross roads without the need for traffic lights. In Japan too, traffic regulations were amended, with the introduction of roundabout intersections. Subsequently, traffic regulations were enforced at roundabout intersections on September 1, 2014. The difference between roundabout intersections and crossroad intersections is based on how a vehicle enters and leaves an intersection. Specifically, the movement of a vehicle consists of two stages—entry into the intersection and exit from the intersection at a crossroad. On the other hand, at a roundabout intersection there are three stages, inflow into the roundabout, going around the central junction, and outflow from the roundabout. It is necessary to develop design guidelines that fully take into account the features of roundabout intersections and crossroad intersections. At present, when a roundabout is built, the lighting is designed based on guidelines meant for a crossroad intersection. However, that is dangerous for users because the specific requirements of a roundabout intersection are not taken into consideration. In previous papers, there have been many studies on traffic flow and vehicle behavior at a crossroad intersection. However, there are no studies that examine the relationship between the physical environment, i.e., the lighting at a roundabout intersection and the visibility of a driver at night.
 In this study, experiments were conducted in varying viewing conditions at night at the Hitachi Taga roundabout intersection in Hitachi City, Ibaraki Prefecture. Apart from this, visibility evaluation experiments were also conducted in varying lighting conditions. The following three findings were thus obtained on the role of lighting in illuminating a pedestrian to a driver entering and exiting a roundabout intersection at night. In this study, we conducted a visibility evaluation experiment in which the illumination conditions were changed in the case of changing the condition of the viewing subject at the Hitachi Taga circular intersection in Hitachi City, Ibaraki prefecture, at night, and in the nighttime experimental street, and the influx of the roundabout intersection At the time of departure, the following findings were obtained on the influence of nighttime lighting on the visibility of crosswalkers viewed from the driver.

 1. Drivers' visibility of crossing pedestrians under crosswalk lighting was observed at the time of traffic inflow into and out of the roundabout intersection. In addition, the effect of a crossing pedestrian wearing a reflector at an illuminated roundabout intersection was noted. Visibility was also checked when there was no light to illuminate the crossing pedestrian wearing a reflector. However, the effect of lighting on the ability of a driver to see a pedestrian could not be established.The visibility of the right crosswalker waiter is lower at the time of inflow when turning to the left at the annual intersection at night as compared with the left side crosswalk waiting person as seen from the driver.
 2. When a driver enters a roundabout intersection at night and immediately turns left, walkers on the right side are less visible than those on the left.
 3. When the driver circumvents the roundabout after turning left, walkers on the left are less visible than those on the right.

 These findings should be taken into consideration to frame new lighting design guidelines for roundabout intersections.

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In Making Mark Twain Work in the Classroom, Twain's scholars and educators introduce different ways of promoting the students' motivations to approach Twain's works. However, they do not discuss how the students' experience of watching the dramatized versions of his works on stage would affect the students' interest in reading his works. In his interview on the significance of children's appreciation of theatre as the audience, Asaya Fujita, a playwright and director, points out that children's seeing plays on stage is crucial to their human development. "Watching a play helps you find out about yourself," Fujita says. In this paper, I would like to examine the Deaf West Theatre production of Big River, a muscial adaptation of Twain's Adventures of Huckleberry Finn, first performed in October, 2002. I would discuss how their theatrical work would inspire the students' imagination on Twain's literary world and would enhance students' better understanding of art, literature and intercultural communication.

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過飽和ネットワークを対象とする交通制御には，無秩序に進展する待ち行列の挙動とドライバーの経路選択行動を考慮した動的な制御手法が必要である．本研究では，まず制御の時間遅れ性に着目し，過飽和ネットワークを対象とする交通制御が満たすべき性質を整理する．次に，道路ネットワーク中の閉ループ構造に着目し，閉ループ中を延伸する待ち行列に起因するグリッドロック現象の発生条件を示す．これらの条件を考慮して，モデル予測に基づいて総旅行時間を最小化する交通制御アルゴリズムを提案し，ドライバーの経路選択行動について二通りのシナリオを考えた数値実験によって提案手法の有効性と課題を示す．

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