S f l d i i tt tiSafer glances, driver inattention, and crash risk in lead-vehicle

followingTrent Victor,

Jonas Bärgman, Christian-Nils Boda, Marco Dozza, Johan Engström, Carol Flannagan, John D. Lee, Gustav Markkula

SHRP2 Summer Symposium Final Report Presentation 10 July, 2014

Research Question

What is the relationship between driver inattention and crash risk in lead-vehicle pre-crash scenarios (rear-end crashes)?

Final Sample Size

• 46 crash events

• 211 near-crash events257

High degree ofmatching on: driver,

trip, no standstill, trafficflow, intersections,

speed, weather, day/night, etc

Controls in case-crossover approach.

• 257 matched baseline events

• 260 random baseline events Completely random, different drivers, trips

etc.

Controls in case-control approach.

Distracting activities 5s before Precipitating Event to 1s after

** *** *

Reduced risk from Talking/listening:• Not because of NC, nor commercial

drivers, nor poor baseline matching, nor drowsiness, nor gaze concentration.

• No slower reactions. • We propose the task & glance

displacement explanation

What are the most dangerous glances away from the road, and

what are safer glances?

Glances Only

Eyes off path more in 6s window at the Precipitating Event (replication)

>2s Klauer Present (2010) results

Matched BL (cond) 1.6 2.1Random BL (crude OR) 2.1 2.0

Eyes off Path before Crash/minTTC

Crash/Crash/minTTC

Precipitating Events= Lead Vehicle Brake Light Onset

Glance locations before Crash

Glance locations before Near Crashes (minTTC)

Glance locations in Matched Baselines

Glance locations in Random Baselines

Off-Path Glance Duration Distributions

= Proportion of eyes off path 3-1s before C/NC

= Mean single glance duration

−12 −8 −4 0Time from TTCmin at 0 seconds

Unc

erta

inty

and

eye

s of

f roa

d

= Mean level of uncertainty (Senders et al, 1967)22.2

Glance metrics are powerful predictors

• No substantial cumulative effect from segments before Off3to1. The EOP peak is what matters.

• A glance model based on a linear combination along with the interactions was most predictive of crashes and near crashes. It combined:

• Off3to1 (Proportion of eyes off path 3-1s before crash/minTTC, equivalent to the Percent Road Center metric)

• mean.off (mean single glance duration) • m.uncertainty (mean level of uncertainty)

What are the most dangerous glances away from the road, and what are safer

glances?

Adding lead-vehicle kinematics

+

How does the timing of lead-vehicle closing kinematics in relation to off-road

glances influence crash risk?

How drivers are tricked into rear-end crashesLead vehicle

brake light turnson. Don’t have an

effect. Cry wolfeffect.

Driver looks away from road whenno looming

Fast looming duringglance away

(fast invTTC changerate)

Eyes on

Date Created: [YYYY-MM-DD]

Issuer: [Name] [CDS-ID]; [Organisation]; [Name of document]; Security Class: [Proprietary]

17

Crash occurs

Eyes off

PE

The Mismatch Mechanism:

Eyes off LoomingCategory 1, Inopportune

glances(eyes off threat)

Category 2, Looking away in

an alreadycritical situation (eyes off threat)

Fastchange

Category 3, Looking away and back again before the situation has

turned critical(eyes on threat)

Slowchange

Short Glance

LongGlance

Category 1. Inopportune glance

Eyes on

Figure 9.8 Example of a Categry 1 crash (event ID 19147492)

Eyes off

Category 2. Looking away in an already critical situation

Figure 9.9 Example of a Categor 2 crash (event ID 19147617)

Category 3. Looking away and back again before the situation has turned critical (eyes on

threat)

Figure 9.10 Example of a Category 3 crash (event ID 19147493)

What are the most dangerous glances away from the road, and what are safer glances? How does the timing of lead vehicle closing kinematics in relation to off-road glances influence crash risk?

• Probability for mismatch depends on the joint probability distributions of glance durations and situation kinematics.

• Dangerous glances are those during which the driver gets exposed to the risk of a rapidly changing situationg g

• An off-road glance is safe when the safety margins adopted are sufficient to protect if the situation changes rapidly during the glance.

• A combination of 3 glance metrics strongly predicted CNC risk.• No substantial cumulative effect from time segments before the EOP peak• The majority of crashes were associated with glances shorter than 2s

Countermeasures?Countermeasures?

• Eliminating glances above a limit of 2 seconds will not eliminate the problem. Majority of crashes were associated with short glances.

• Efforts should focus on minimizing eyes off path glances to portable electronic devices, as they are clearly more assiated with risk than vehicle-integrated systems.

Human-Machine Interaction design, distraction guidelines, and other regulatory agency

countermeasures.

• Results support the potential for non-visual interfaces, as Talking/listening on a cell phone was reduced risk.

• See distraction as a joint probability problem

• Active Safety systems provide the safety margins needed to protect the driver if the situation changes rapidly during an off-path glance.

– Emergency braking (AEB), Forward Collision Warning (FCW), Adaptive Cruise Control (ACC), V2V

Vehicle design and driving support

Glance Length

Freq

uenc

y

Approximately:

V2V– More time headway, active braking (emergency

or continuously), and warnings

• Supports the need for inattention sensing (e.g. eyetracker) and its use to warn the driver of inattention mismatches, as applied to active safety systems.

• Points to improved braking performance and road surfaces

0s 1s 2s 3s

• Public awareness of mismatch mechanism• Teach importance of adopting safe headways• Performance based insurance• Particular importance in 16-17yr olds and 76+

Education and Behavioral Change

• Reduce disruptive, erratic traffic flows. Create smooth flowing traffic, reduce the occurence of sudden, unexpected kinematic changes.

• Improved road surfaces decrease stopping distance• Self-explaining roads needed

Road and Infrastructure design

End

Risk at the Precipitating Event

(=LV Brake Light Onset)

Significant age differences in crashes

76+

16-17

Significantly more visual obstructions and rain in crashes

Rain

Looming (invTTC) at Start and End of Last Glance

Figure 9.4 Inverse time-to-collision (invTTC) at the onset and offset of the last glance

Short Headway at Start of Last Glance

Reaction depends on when the driver looks back and looming (invTTC)

0 8

1

1.2

1.4

1.6

river

reac

tion

(1/s

)

Crashes (n = 34)

0 8

1

1.2

1.4

1.6

river

reac

tion

(1/s

)

Near-crashes (n = 117)

-0.5 0 0.5 1 1.50

0.2

0.4

0.6

0.8

invTTC at end of last off-path glance (1/s)

invT

TC a

t dr

-0.5 0 0.5 1 1.50

0.2

0.4

0.6

0.8

invTTC at end of last off-path glance (1/s)

invT

TC a

t dr

Figure 9.13. InvTTC at end of last off-path glance (invTTCELG) versus invTTC at driver reaction (invTTCR), for crashes and near-crashes. In the right panel, four red rings show driver reactions in the four near-crashes where the driver talked or listened on cell phone.

Brake lights have a limited effect

• Seeing brake lights turn on does not have an effect on outcomes. Cry wolf effect.– Drivers who crashed were more likely to look ahead when brake

lights turned on. Example crashes:

What crash severity scale is best suited for analysis of risk?

• Use at least DeltaV for crashes, use minTTC for near crashes. • Model-estimated Injury Risk index (MIR) and Model-estimated Crash Risk index

(MCR) can be used in many new ways. More work needed.