January 8, 2020
1. Rapid technological advancements in the middle of 20th century have led to the idea that one
needs to “design a human to fit the machine”. Describe what is meant by this principle. Explain
whether it is consistent with the human factors’ approach.
“Human to fit the machine” principle means that the design of technology is left to engineers.
This can result in sophisticated systems from the technological point of view, but the human
users are not taken into account, or not taken into account enough. According to this principle,
human users are presented with technology and have to use it ́as is ́. They need to be selected
or trained or both, in order to be able to operate the machine. Human factors propose a radically
different approach, according to which, technology is designed with a human user in mind and is
taking into account the limitations of the human information processing system. This latter
approach has led to a significant reduction of accidents and improved used of technology.
2. In some countries (e.g., USA, Japan) you may find a horizontally oriented traffic light with a
green light on the left (see below).
a. A traffic user from Europe will have difficulties with this traffic light. Name which design
principle is violated.
Consistency principle is violated. This horizontal orientation is inconsistent with user’s
experience with a vertically oriented traffic light.
b. A color-blind person from Europe might not be able to use this traffic light without an
explanation, while he/she can use the vertically oriented one in Europe without a
problem. Which design principle ensures that this is possible?
Redundancy gain principle. Position and hue are redundant in the European design, with each
signal coded by both. Color-blind person can use the vertical traffic light, but has to learn where
the green light appears in the new design and whether it is redundantly coded, in order to start
using it.
3. In technical and scientific literature the sizes of visual stimuli are often reported in degrees of
visual angle, and not in cm or inches.
a. Why is the measure of visual dimensions in degrees of visual angle preferred?
, The measure in degrees of visual angle is preferred because it provides an estimate of the size
of the projection of an object onto the retina, e.g., the retinal size of the object. This is important,
since the retinal size is dependent on the distance between the observer and the object.
Reporting only the object size in cm, without the distance from the observer is not sufficient for
replicating the measurements. Visual angle provides a single metric for reporting the object size
and allows for replication of the measurements.
b. Draw the visual angle of the flower in the figure below
→
c. How is it computed? Hint: the approximation formula is sufficient.
Visual angle = Object Size/distance from observer. To convert the radians to degrees multiply by
180/pi.
4. Driving is a complex task, but with the help of task analysis it can be decomposed into 3 main
subprocesses as indicated below. Provide an example for each subprocess.
a. Strategy: route planning and choice
b. Tactics: Changing lanes, deciding to overtake
c. Vehicle control: Longitudinal (distance from the car upfront) and Lateral (staying in the lane)
5. What is the main difference between the closed-loop and open-loop control?
In a closed loop the operator adjusts the control based on the negative feedback from his/her
actions (prediction error). He continuously monitors the feedback and adjusts performance
accordingly. In the open look the operator does not pay attention to the feedback but possesses
advanced knowledge or experience to be able to access the situation and choose the right
course of action.
6. We live in times when more and more tasks performed by a human are automated. Give
three reasons why a certain task should be automated (for example, the three Ds mentioned in
the lecture):
1. Dull – baggage screening at the airport
2. Dirty – sorting garbage
3. Dangerous – working at the nuclear plant
1. Rapid technological advancements in the middle of 20th century have led to the idea that one
needs to “design a human to fit the machine”. Describe what is meant by this principle. Explain
whether it is consistent with the human factors’ approach.
“Human to fit the machine” principle means that the design of technology is left to engineers.
This can result in sophisticated systems from the technological point of view, but the human
users are not taken into account, or not taken into account enough. According to this principle,
human users are presented with technology and have to use it ́as is ́. They need to be selected
or trained or both, in order to be able to operate the machine. Human factors propose a radically
different approach, according to which, technology is designed with a human user in mind and is
taking into account the limitations of the human information processing system. This latter
approach has led to a significant reduction of accidents and improved used of technology.
2. In some countries (e.g., USA, Japan) you may find a horizontally oriented traffic light with a
green light on the left (see below).
a. A traffic user from Europe will have difficulties with this traffic light. Name which design
principle is violated.
Consistency principle is violated. This horizontal orientation is inconsistent with user’s
experience with a vertically oriented traffic light.
b. A color-blind person from Europe might not be able to use this traffic light without an
explanation, while he/she can use the vertically oriented one in Europe without a
problem. Which design principle ensures that this is possible?
Redundancy gain principle. Position and hue are redundant in the European design, with each
signal coded by both. Color-blind person can use the vertical traffic light, but has to learn where
the green light appears in the new design and whether it is redundantly coded, in order to start
using it.
3. In technical and scientific literature the sizes of visual stimuli are often reported in degrees of
visual angle, and not in cm or inches.
a. Why is the measure of visual dimensions in degrees of visual angle preferred?
, The measure in degrees of visual angle is preferred because it provides an estimate of the size
of the projection of an object onto the retina, e.g., the retinal size of the object. This is important,
since the retinal size is dependent on the distance between the observer and the object.
Reporting only the object size in cm, without the distance from the observer is not sufficient for
replicating the measurements. Visual angle provides a single metric for reporting the object size
and allows for replication of the measurements.
b. Draw the visual angle of the flower in the figure below
→
c. How is it computed? Hint: the approximation formula is sufficient.
Visual angle = Object Size/distance from observer. To convert the radians to degrees multiply by
180/pi.
4. Driving is a complex task, but with the help of task analysis it can be decomposed into 3 main
subprocesses as indicated below. Provide an example for each subprocess.
a. Strategy: route planning and choice
b. Tactics: Changing lanes, deciding to overtake
c. Vehicle control: Longitudinal (distance from the car upfront) and Lateral (staying in the lane)
5. What is the main difference between the closed-loop and open-loop control?
In a closed loop the operator adjusts the control based on the negative feedback from his/her
actions (prediction error). He continuously monitors the feedback and adjusts performance
accordingly. In the open look the operator does not pay attention to the feedback but possesses
advanced knowledge or experience to be able to access the situation and choose the right
course of action.
6. We live in times when more and more tasks performed by a human are automated. Give
three reasons why a certain task should be automated (for example, the three Ds mentioned in
the lecture):
1. Dull – baggage screening at the airport
2. Dirty – sorting garbage
3. Dangerous – working at the nuclear plant
