駕駛注意力分配模式

Abstract

注意力分配為行車安全的重要關鍵，駕駛人必須將其有限資源妥適分配至車輛前方、車內與車外等區域，以維持適當之情境察覺，並得與前車保持安全距離。然而過去對於注意力分配之研究多侷限於對各焦點的總體分析，無法探究其個體行為特性，此外，對於視線移轉過程之呈現方式往往過於著重於「前方」焦點，致使研究成果當中的多數路徑皆為移往或來自前方，此一現象導致研究無法完整呈現駕駛人視線移轉的完整過程，因此，如何呈現注意力分配以及分析其特性為事故分析與防範的重要基礎，唯有提出適切的量化方法，才能正確呈現駕駛人移轉注意力之過程。 以注意力分配為題，本研究欲回答下列問題：1) 駕駛人注意力分配應如何呈現？ 2) 駕駛人是否會採取特定的注意力分配型態？ 3) 若有，有哪些型態？ 4) 有哪些變數會影響駕駛人注意力分配？為回答上述問題，本研究首先提出「注意力分配循環」之概念，以前方焦點視為一基準點，將視線移開前方至他處最後再回到前方的循環過程視為注意力分配之基本元件，呈現駕駛視線分配的完整過程。本研究於分析階段採用美國100-car自然駕駛資料庫當中的事件資料庫進行分析，透過序列關聯法則，找出駕駛人將視線在前方與非前方之間移轉的路徑，並透過羅吉特模式之應用，計算駕駛人在不同狀況下，選擇不同類型視線移轉與選擇各焦點的機率分配。 研究結果發現，研究發現超過90%以上的注意力分配循環僅包含一個非前方焦點，亦即當駕駛人將視線移開時，多數僅會注視一個非前方焦點 (以車內分心、左後視鏡與車內後視鏡為主)，以避免因移開視線時間過長而無法觀察前方路況之狀況發生；本研究亦發現駕駛人會將視線在前方與同一焦點間來回移轉，此特性尤以車內後視鏡與車內分心最為明顯，顯示駕駛人於該二焦點收集資訊時，會不斷將視線移回前方，以確保將視線移開前方的過程中仍可維持對前方的情境察覺能力。此外，駕駛人會避免將視線直接自一非前方焦點轉移至另一非前方焦點，而是先將視線移回前方再移往下一焦點，以確保車前安全。駕駛人選擇焦點時，傾向將視線分配至較近、對安全影響較大、較明亮且資訊出現頻率較高的焦點上。 最後，本研究將注意力分配循環之概念應用於安全評估，並以駕駛反應時間為基礎，設定駕駛人得以將視線移開前方的最長時間。研究發現，當駕駛人連續注視的焦點數越多時，其無法觀察前方路況的總時間越長，因此，對前方刺激的餘裕反應時間越短；其中，分心、駕駛操作意向等因素皆會影響其實際的反應時間長度。若以注意力分配角度出發檢視，目前現行之2.5秒反應時間設計標準已無法滿足現況，若以90百分位為基準，道路設計應將反應時間設定為3秒。 囿於資料限制，本研究所引用之資料雖無法代表駕駛人的典型注意力分配型態，然而所提模式與其結果仍可提供後續分析探討之參考，並可作為事故防範與安全分析之用，此一領域仍待後續進一步探討。

Attention allocation is the key of driving safety, which relies on the adequate distribution of the driver’s attention to the forward area and to other non-forward focal points. However, most representation of attention allocation are the aggregated result of vision transition. It is not able to observe drivers’ microscopic behavior against dynamic changing environment. Moreover, thus far, current methods seem to be over-emphasized on the dominant forward area, causing the observed paths were mostly ones shifting from or heading to the frontal side. The whole process of transiting vision among focal points cannot be observed. Consequently, a mechanism for attention allocation is a critical issue in crash prevention. There are four questions that this study aims to answer: 1) How is driver attention allocation represented? 2) Do patterns of driver attention allocation exist? 3) If yes, what are these patterns? and 4) What are the factors affecting driver attention allocation? To answer these questions, this study proposes the concept of renewal cycle, which is the entire process of drivers glancing at forward side, transiting vision away, and finally transiting vision back to the front. Using the renewal cycle as the basic component of attention allocation analysis, this study is able to represent drivers’ vision transition in a more realistic way. In the section of empirical analysis, this study adopted the event database of 100-car naturalistic driving studies. Sequential rule mining and multinomial logit model were used for generating the patterns and probability of drivers transiting vision among focal points. This study found that over 90% of drivers’ attention allocations were 2-glance renewal cycles, suggesting that drivers usually glance only one off-road focal point, among which the in-vehicle distraction, left mirror and rearview mirror are the three most frequent appeared ones. Among these 2-glance renewal cycles, some were found repeatedly appeared several times, particularly the ones related to in-vehicle distraction and rearview mirror. It suggests a compensation of lost awareness against leading area by separating their long glance off-road into several shorter ones. In addition, drivers prefer not to transit vision from one non-forward focal point directly to another. Instead, they glance at forward side between two non-forward glance for checking the timely status ahead. As for the choices of focal points, four constructs of attributes (Salience, effort, expectancy and value) in SEEV model were included in this model. The result shows that drivers would allocate more attention to the focal point with higher information expectancy and value. On the other hand, less salient and higher effort would inhibit the vision transition. Finally, this study adopted the Perception Reaction Time (PRT) as the reference for setting the maximum time for drivers to transit vision away from the frontal side. It clearly indicated that drivers glancing consecutively at more non-forward focal points in a sequence were more likely to have insufficient time for responding to harmful changes in front of them. In addition to distractions, maneuver intentions, number of glances in a renewal cycle, and their interactions all significantly affected drivers’ attention allocation. As for the current 2.5-s PRT rule, it may not be robust enough to satisfy every situation. Based on the results derived from the 100-car event database, a 3.0-s PRT may be better for designing safer roads. Although the sample drivers adopted in this study were not representative, the preliminary research results were promising and fruitful for potential applications, particularly educating novice drivers. These findings might have striking implications for accident prevention. This area of study deserves further attention.