Traffic Psychology
Task Capability Interface Model - Answer-Using models to explain driver behaviour
1. perception
2. expectation
3. judgement
4. memory
5. decision/planning
6. car handling/driver action
7. errors, assesment, and conclusion
8. rating of complexity
9. assesment of risk
Task Capability Interface
Important concepts:
Driver Capability - Answer-how competent is the driver
Task Capability Interface
Important concepts:
Loss of control - Answer-how demanding it is to complete driving related behaviour e.g. steering car
round a corner
Task Capability Interface
Important concepts:
,task demand - Answer-impact depends on driving situation: stalling the engine vs crashing at speed
Task difficulty - Answer-Task difficulty = task demand - driver capability
TDi= TDe - DC
Since capability is reasonably constant, as TDe increases so TDi increases
For an experienced driver with high Capability = ______
For an inexperienced driver with low Capability = _______ - Answer-low TDi
high TDi
As TDe ↑, - Answer-spar capacity ↓ and driver becomes more vulnerable to error or the increased
demands of emergency situations
Using a mobile when driving on straight road remains within driver's capability but as soon as when TDe
= responding to pedestrian crossing the road + demand of phone use TDe > DC resulting is loss of control
Exceeding threshold TDi - Answer-Current TDe can be increased as the driving task becomes more
complicated in an expected fashion e.g. route requires navigation of a complex junction
TDe increased due the addition of an unexpected additional task e.g. having to brake due to car in front
suddenly braking
DC becomes impaired e.g. due to alcohol consumption
components of task demand (TDe):
Information input - Answer-interpreting the road environment ahead
components of task demand (TDe):
response output - Answer-manoeuvring of car in appropriate fashion
,Components of TDe
Contributed to by factors including - Answer-vehicle performance, instrument display characteristics,
ergonomic match between car and driver, route, physical characteristics of the road and the presence
and behaviour of other road users
Can be reduced by technology such as lane assist
Default method of reducing TDe is to reduce speed
Important element is time to execute a behaviour/response
The lower the required response window the greater the TDe
Is contributed to by factors such as: physiological status, training, knowledge and experience
Experience allows for the development of schemas to facilitate efficient navigation of scenarios
previously encountered
Enables preadaptation to anticipated changes in TDe in a top down fashion
conscious processing - Answer-Many errors, slow, mutual interference between simultaneous processes
Serial in nature
Great range of contents, great ability to relate different conscious contents to each other
Requires effort
unconscious processing - Answer-Few errors, high speed, little mutual interference
Parallel in nature
Limited range of contents, routines are relatively isolated and autonomous
Appears to require little or no effort
Components of DC - Answer-As the balance of Conscious processes relative to unconscious processes
increase so TDi increases (Fastenmeier & Gstalter, 2007)
, When learning to drive driving is primarily at the conscious level and is the reason why the task is so
difficult
Through skill acquisition/learning task execution switches from conscious to unconscious thus making
the task less difficult
Task Difficulty Homeostasis - Answer-Central principle - drivers are continually making real time
decisions to maintain perceived task difficulty within acceptable levels usually through speed
adjustments
Increases in TDe produced by darkness (Kilpeläinen & Summala, 2007) or mobile phone use (Liu & Lee,
2005) results in proportional decrease in speed
Means that as TDe decreases with empty roads speed will increase (Broughton, 2005)
TDe could also be decreased by increasing headway to car in front
calibration - Answer-Young drivers particularly overestimate their capability (De Craen, Twisk,
Hagenzieker, Elffers, & Brookhuis, 2011)
Young Drivers tend to operate at a lower safety margin - Patten, Kircher, Ostlund, Nilsson, & Svenson
(2006) found that YDs took longer to respond to a secondary detection task while driving in a simulator
than more experienced drivers
Saad, Delhomme & van Elslande (1990) found that YDs reduced their speed less when approaching a
junction
Evidence for TDiH (task difficulty homeostasis) - Answer-Horst (2007) found that when drivers were
asked to brake hard to stop in front of simulated vehicle, time to stop was consistent independent of
approach speed
Stradling et al. (2008) found wide variation in normal speed for a single carriageway rural road and the
speed that would put them right at edge of safety margin
Consistent relationship between the two speeds with the later representing on average a 14% increase
Feeling of risk (proxy of TDi) was independent of speed indicating a consistency of TDi across drivers
Fuller et al. (2008) found 4 types of driver - Answer-Low risk threshold (40%) generally comply with
speed limits
Task Capability Interface Model - Answer-Using models to explain driver behaviour
1. perception
2. expectation
3. judgement
4. memory
5. decision/planning
6. car handling/driver action
7. errors, assesment, and conclusion
8. rating of complexity
9. assesment of risk
Task Capability Interface
Important concepts:
Driver Capability - Answer-how competent is the driver
Task Capability Interface
Important concepts:
Loss of control - Answer-how demanding it is to complete driving related behaviour e.g. steering car
round a corner
Task Capability Interface
Important concepts:
,task demand - Answer-impact depends on driving situation: stalling the engine vs crashing at speed
Task difficulty - Answer-Task difficulty = task demand - driver capability
TDi= TDe - DC
Since capability is reasonably constant, as TDe increases so TDi increases
For an experienced driver with high Capability = ______
For an inexperienced driver with low Capability = _______ - Answer-low TDi
high TDi
As TDe ↑, - Answer-spar capacity ↓ and driver becomes more vulnerable to error or the increased
demands of emergency situations
Using a mobile when driving on straight road remains within driver's capability but as soon as when TDe
= responding to pedestrian crossing the road + demand of phone use TDe > DC resulting is loss of control
Exceeding threshold TDi - Answer-Current TDe can be increased as the driving task becomes more
complicated in an expected fashion e.g. route requires navigation of a complex junction
TDe increased due the addition of an unexpected additional task e.g. having to brake due to car in front
suddenly braking
DC becomes impaired e.g. due to alcohol consumption
components of task demand (TDe):
Information input - Answer-interpreting the road environment ahead
components of task demand (TDe):
response output - Answer-manoeuvring of car in appropriate fashion
,Components of TDe
Contributed to by factors including - Answer-vehicle performance, instrument display characteristics,
ergonomic match between car and driver, route, physical characteristics of the road and the presence
and behaviour of other road users
Can be reduced by technology such as lane assist
Default method of reducing TDe is to reduce speed
Important element is time to execute a behaviour/response
The lower the required response window the greater the TDe
Is contributed to by factors such as: physiological status, training, knowledge and experience
Experience allows for the development of schemas to facilitate efficient navigation of scenarios
previously encountered
Enables preadaptation to anticipated changes in TDe in a top down fashion
conscious processing - Answer-Many errors, slow, mutual interference between simultaneous processes
Serial in nature
Great range of contents, great ability to relate different conscious contents to each other
Requires effort
unconscious processing - Answer-Few errors, high speed, little mutual interference
Parallel in nature
Limited range of contents, routines are relatively isolated and autonomous
Appears to require little or no effort
Components of DC - Answer-As the balance of Conscious processes relative to unconscious processes
increase so TDi increases (Fastenmeier & Gstalter, 2007)
, When learning to drive driving is primarily at the conscious level and is the reason why the task is so
difficult
Through skill acquisition/learning task execution switches from conscious to unconscious thus making
the task less difficult
Task Difficulty Homeostasis - Answer-Central principle - drivers are continually making real time
decisions to maintain perceived task difficulty within acceptable levels usually through speed
adjustments
Increases in TDe produced by darkness (Kilpeläinen & Summala, 2007) or mobile phone use (Liu & Lee,
2005) results in proportional decrease in speed
Means that as TDe decreases with empty roads speed will increase (Broughton, 2005)
TDe could also be decreased by increasing headway to car in front
calibration - Answer-Young drivers particularly overestimate their capability (De Craen, Twisk,
Hagenzieker, Elffers, & Brookhuis, 2011)
Young Drivers tend to operate at a lower safety margin - Patten, Kircher, Ostlund, Nilsson, & Svenson
(2006) found that YDs took longer to respond to a secondary detection task while driving in a simulator
than more experienced drivers
Saad, Delhomme & van Elslande (1990) found that YDs reduced their speed less when approaching a
junction
Evidence for TDiH (task difficulty homeostasis) - Answer-Horst (2007) found that when drivers were
asked to brake hard to stop in front of simulated vehicle, time to stop was consistent independent of
approach speed
Stradling et al. (2008) found wide variation in normal speed for a single carriageway rural road and the
speed that would put them right at edge of safety margin
Consistent relationship between the two speeds with the later representing on average a 14% increase
Feeling of risk (proxy of TDi) was independent of speed indicating a consistency of TDi across drivers
Fuller et al. (2008) found 4 types of driver - Answer-Low risk threshold (40%) generally comply with
speed limits
