Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk (2014) / Chapter Skim
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65 C h a p t e r 7 This chapter examines the research question, How does the timing of lead-vehicle closing kinematics in relation to offroad glances influence crash risk? The previous chapters have demonstrated, in line with existing results (e.g., Klauer et al.
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66 criticality of the situation developed while looking away. Furthermore, to what extent did the duration of the last glance influence the event outcome?
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67 off-path glance in 23% of the crashes, 34% of near crashes, and 31% of matched baselines. This comparison thus includes co-occurrence of Eyes off Path with any brake light onset in the 8-second time window.
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68 indicating that the drivers generally ignored this predictive information. Moreover, a significant proportion of these drivers even looked away from the road just after having seen the brake lights illuminate.
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69 situations in which the subject vehicle closes in rapidly on the lead vehicle, but at a larger distance than in crash and near-crash situations. The distributions of relative velocity at LG end indicate a strong average change in relative speed during the last glance away, both for crashes [t(35)
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70 headway when the drivers looked away are very similar for all three event types (with no statistically significant differences between the means)
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71 while the driver is looking away from the forward path. When the last glance is initiated, the situation is generally still kinematically similar to a normal following situation and the driver considers it safe to look away.
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72 the mean LG duration and invTTC change rate are both higher for crashes than for near crashes although the distributions overlap considerably. The multivariate logistic regression analysis assesses the effect of last glance duration and the invTTC change rate on the likelihood of a crash/near crash relative to the matched baselines.
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73 shows is that, given that the driver looks away from the road within the 8 seconds before the crash, the risk that the event develops into a crash or near crash is mainly determined by the interaction of invTTC change rate and last glance duration. To gain further insight into this interaction between LG duration and the invTTC change rate during the last glance, the two variables were plotted against each other, as shown in Figure 7.8.
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74 grow above zero. There was most often a strong violation of expectations; these events often occurred at junctions when the principal other vehicle (POV)
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75 look away at all within the 8-second window (these were excluded in the present analysis, as explained above)
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76 does not apply to cut-in scenarios, which were excluded from the present analysis. What determines the location of the critical boundary for the Category 1 crashes?
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77 First, consider the actual driver reaction points (the black crosses)
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78 referred to as eyes-on-threat events, in line with the conclusion above in this chapter that in the Category 3 crashes, the rear-end threat arose after the last off-path glance.
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79 Figure 7.13. As in Figure 7.12, but showing only events with one or more brake light onsets between end of last glance and the driver reaction point.
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80 invTTC was the same at end of last glance and reaction. As in Figure 7.12, there are signs of qualitative differences between eyes-on-threat and eyes-off-threat events, and there are traces of the same 0.2 s-1 threshold for invTTCR.
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81 has risen above a threshold At. Here invTTC is used, but inverse Tau could equally be used.
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82 As a contrast to the accumulator model, another twoparameter model was also fitted that predicts a driver reaction and a fixed reaction-time delay TR after passing an invTTC threshold. At long times to reaction, this model closely approximates the accumulator model (with M as the invTTC threshold, and accumulation to At as a delay)
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83 with short times to reaction, the model fitted to near crashes predicted faster reactions than the model fitted to crashes, and the average difference of 0.22 seconds is well in line with the 0.19 seconds difference observed in relation to Figure 7.12. For the eyes-on-threat crashes, with longer times to reaction, prediction deviations went in both directions, adding up to the near-crash model predicting, on average, 0.01-second shorter times to reaction.
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84 from comparable near crashes may be related to failures to apply crash-avoidance braking or steering maneuvers after the point of driver reaction. This could involve differences in the time from observed driver reaction (such as studied here)
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85 2013) , in which the duration of the last glance and the invTTC change rate combine into a "perfect mismatch" that produces the crash.
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