Effects on driving behavior of congestion
information and of scale of in-vehicle
navigation systems
Author: Shiaw-Tsyr Uang, Sheue-Ling Hwang
Transportation Research Part C 11 (2003) 423–438
Reporter: Yang Kun Ou
Purpose

The purpose of this research was to compare
the usage of a traditional paper map and
electronic route maps during driving, and to
consider the effects of congestion information
and map scale sizes on driving performance,
workload and subjective feelings.
Reference


When one driver is driving in familiar areas, s/he
often navigates from the origin to the destination
according to his or her pre-built cognitive map.
Navigation, in this case, depends mostly on route or
survey knowledge rather than landmark knowledge
(Wickens, 1992).
drivers who were familiar with the road network had
less difficulty in finding destinations and drove
shorter duration routes than drivers who were
unfamiliar with the road network (Eby and Kostyniuk,
1999).
Reference

Hughes and Cole (1986) have found that from
30% to 50% of drivers visual attention may be
allocated to things unrelated to the driving task,
and thus using the electronic map while
driving is not necessary to decrease driving
performance.
Reference

when information complexity increases, the
drivers glance duration and frequencies
increase, and thus increase the potential
driving hazard and/or driver workload
(Dewar, 1988; Dingus and Hulse, 1993;
Wierwille, 1993)
Methods of the Experiment I

Subjects
• A total of 20 undergraduate students (15 males and
5 females).
• Half of the participants had drivers licenses
• Subjects age ranges from 20 to 23 years old
(mean=22, SD=0.97)
• Subjects reported they understand the experimental
procedures completely (mean=1.40, SD=0.82) and
highly devoted themselves to the experimental
tasks (mean=1.45, SD=0.76)
Apparatus

The driving simulator

17-in & 14-in color monitor

The Virtual environment development software
(3D Webmaster version 5.5)
Experimental design


Two within-subjects factors (availability of congestion
information and scale sizes) were used to construct four
electronic route map conditions in this study
• map A as small-scale without congestion information
• map B as small-scale with congestion information
• map C as large-scale without congestion information
• map D as large-scale with congestion information
A traditional paper map usually without congestion
information was also used as one of the map conditions.
Experimental design cont.



All subjects experienced these five conditions
in a randomized sequence to counterbalance
the possible learning or fatigue effects.
Five conditions were tested in different driving
scenarios to avoid memory effects
These five driving scenarios have equal trip
length
Independent variables

The independent variables of the present study were
the availability of congestion information and the
scale sizes of maps
• A large-scale map could display the view of 3–4
blocks
• A small-scale map showed the view of nearly two
blocks
Dependent variables


The criteria of driving performance were trip
duration, driving speed, number of navigation
errors
Included heart rates to represent the degrees of
workload (Myrtek et al., 1994) and subjective
ratings to show perceived nervousness, fatigue
and task difficulty toward different experimental
conditions. (Likert-type scale)
Result
A traditional paper map vs. electronic maps


The paired t tests were conducted to compare the
subjective feelings between using a paper map and
using four electronic maps.
No significant difference was found between the
paper and electronic maps
• (t =0:684, 0.428, 0.804, p =0:503, 0.674, 0.431)

The average heart rate when driving and using a
paper map was 80.1 per min, and 79.6 per min when
deiving and using electronic maps
Result
A traditional paper map vs. electronic maps


the driving performance of using a paper map and
the average driving performance of using four
electronic maps.
The results revealed that there was no significant
difference in trip duration and driving speed
while using these two kinds of maps during
driving (t=-1.691, 0.655,
p=0.107, 0.520,
respectively).
Result
A traditional paper map vs. electronic maps

One map with an electronic visual display
function will not guarantee its navigation
efficiency, but how an electronic map is
designed and what kind of information is
provided on the map may result in totally
different effects.
Result
Trip duration
 Two significant main effects of congestion
information and scale size were found on trip
duration (F=10.108, 21.450, p=0.005, 0.000,
respectively).
Result

Using electronic route maps with congestion
information may shorten the trip duration than
using those maps without this information

small-scale electronic maps were superior to
large-scale ones in terms of trip duration.
Result

The total number of navigation errors while
using four electronic maps
Result

The average and maximum heart rates while
using four electronic maps
Methods of the Experiment II

The small-scale electronic maps (1–2 blocks)
may have better performance than the largescale ones (3–4 blocks)

The Experiment II was conducted to further
explore the influences of map scale.
Methods of the Experiment II

Subjects
• A total of 18 undergraduate students (9 males and
9 females)
• Eight participants have drivers licenses
• Subjects age ranges from 19 to 23 years old
(mean=21, SD=1.1)
Experimental Procedure

One electronic route map showed the view
within one block, and the other map could
display the view of nearly 1–2 blocks.

Subjects experienced these two conditions in
randomized sequences
Result
• Reducing map scale from 1–2 blocks to less
than one block provides no additional benefits
in consulting the electronic maps and/or
detecting a stimulus.
Discussion

By which the driver may plan the upcoming
maneuvers in advance (Streeter et al., 1985) as well
as build-up route or survey knowledge easily
(Wickens, 1992). In other words, the drivers in past
studies preferred a larger scale

The usage of navigation systems with traffic
congestion information could enhance route selection
quality and result in better driving performance for a
particular driving journey (Stern, 1999)
Conclusion

In-vehicle navigation systems with traffic
congestion information may improve the route
selection quality in terms of shorter trip
duration and fewer navigation errors.