Research on The Effect of Alignments of Mountainous Highways on Driver Characteristics

Li Rongjinga, Mo Qiuyunb, Zhang Keyanc

Guilin University of Electronic Technology, Guilin Guangxi, China

a0500110511@163.com bmoqyun@guet.edu.cn czky1076723530@163.com

Keywords: Mountainous Highways; Heart Rate growth rate; Driver characteristics; HRV

Abstract. Fatigue driving becomes a main hidden danger for traffic safety and endangers people’s

life and property seriously．This paper is to obtain the effect of alignments of mountainous

highways on driver characteristics. this paper combines with all kinds of theoretical methods and

research means on physiology, medical psychology and engineering psychology, then this paper

models regression equation on driver's growth rate of Heart Rate and alignments index of

mountainous highways, and analyses driver's heart rate variability (HRV). The results show that:

when the slope of long downhill is about 3.5%, driver’s growth rate of HR exceeds 40%, which is

the most nervous state. And during the downhill, the value of LF / HF appears to be rising, which

indicates that the more active of the driver’s sympathetic nerve, the more likely to be tired. The

study has a certain realistic guiding significance on mountain highways slop design and fatigue

driving alarm. This acquisition system is easy to operate with high accuracy which can meet the all-

weather, dynamic monitoring and real-time processing requirements. Aim at the national highway

321 that from Guilin to Longsheng, the research on the design and revise of the highway slope has a

certain realistic guiding significance.

Introduction

In today's world, traffic accidents have become a serious social problem, the problem attracts

much attention by every country. Only in the first half of 2011, the national totally reported

1840998 cases of traffic accidents, 1% year - on - year growth, and direct economic loss of 440

million yuan [1]. According to traffic accident statistics on the table 1, it is obviously that road

traffic accidents are growing year by year, which has brought huge influence to the national

economic and social development. Especially, on the high complexity, low level and Western

mountainous regions road, traffic accidents rate is higher. In the western region, the features of the

national highways are mountains around, high fall head, lack of visual range, steep curves. Driving

on this kind of roads, because of long time braking, the car will cause the braking phenomenon of

‘heat fade’, as a result, it will lead to traffic accidents [2]. Therefore, based on real car experiments,

Heart Rate growth rate and heart rate variability will be as the quantified indicators about driver’s

tension and fatigue in the paper. Firstly, the paper makes consideration on highway environments

and alignments. Secondly, the paper makes research on the correlation between alignments index

and the speed, Heart Rate growth rate. In addition, on the long uphill and downhill highways[5], the

mean longitudinal slope of the studied road is above 3%, and the length of continuous downhill is

over 5Km.

Table.1 The traffic accident in recent years[3，4]

Year Traffic accident

（

（（

（frequency）））

） Death tool（

（（

（number）））

） Number of injuries

（

（（

（number）））

）

Direct property losses

（

（（

（hundred million）））

）

2009 238351 67759 275125 9.1

2010 3906164 65225 254075 9.3

Applied Mechanics and Materials Vols. 494-495 (2014) pp 150-154Online available since 2014/Feb/06 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.494-495.150

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.194.20.173, Monash University Library, Clayton, Australia-05/12/14,22:45:19)

Fig.4 Graph of the driver’s heart rate

growth rate changing with slope

Experimental process and data collection

A. The construction of experimental system

A set of acquisition system is self-designed by DAQ card and LabVIEW. As shown in figure 2, the speed and driver’s ECG when driving will get continuously real-time acquisition. The paper chooses van of ‘Wuling zhi guang‘ as the experimental car, and considering the representative of driving experience and driving age, the paper selects different age, driving years, and driving experience to finish the experiment.

Fig.2 Schematic diagram of acquisition system

B. Experimental highway condition and time

In order to make sure the authenticity of experiment and the accuracy of data, the selected experimental roads have the feature of typically western mountain area highway in this study. According to experimental requirements, the paper selects the national highway 321 that from Guilin to Longsheng. Especially on such road as Ding Ling’ao part, K708 +200 le Huang reservoir part in Long Sheng, that is much easy to occur collapse. The elevation of the commanding points in some parts is over 1000m, and the mean elevation is about 800m. Moreover, there always be misty in the spring and winter, and the visibility is very low, so it is prone to emerge accidents on the mountain highways. Above all, the experiment will be hold on in sunny summer day, so as to reduce the influence of temperature, fog and etc.

The analysis upon consistency of the slope with heart rate and speed

A. The long downhill highway

The 321 national highway from Guilin to Longsheng, almost its uphill and downhill is straight, on either its side is mountain and valley, and somewhere the trees are lush, somewhere the trees are few. Therefore, the study of the paper is about straight highway. As shown in figure 3 and figure 4, it is about during the driving of downhill, the changing trend of the driver’s mean speed and mean Heart Rate growth rate, and the highway condition is free stream.

0

10

20

30

40

50

0 1 2 3 4 5 6 7 8

slope(i/%)

t

h

e

s

p

e

e

d

(

υ

/

(

k

m

/

h

)

)

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10

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0 1 2 3 4 5 6 7 8

slope(i/%)

h

e

a

r

t

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a

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o

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(

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/

%

)

From the preliminary qualitative analysis of collected data, fig 3 and fig 4, it turns out that when

driving on the long downhill highway, because of the influences such as braking and others, the slope i and the speed v, the Heart Rate growth rate Ni and HRV are not simply linear relationship. Based on many domestic and international research results, the paper utilizes General Polynomial Fit.vi in LabVIEW to make programming, as shown in fig 5. Respectively upon the slope with the speed and the Heart Rate growth rate is linear fitted, then building regression model.

singal

conditioning

DAQ PC Heart Rate

measuring

approach

Microcontroller

ATMEGA8 Speed sensor

Fig.3 Graph of the speed changing with

slope

Applied Mechanics and Materials Vols. 494-495 151

Fig.5 Liner fitting of slope and car speed

The regression equation about slope and speed:

32 05.0142.135.54.33 iiiv +−+= (1)

The regression equation about slope and Heart Rate growth rate:

32 129.0596.223.1557.2 iiiNi

+−+= (2)

Scope of application of the model: 0<i<8% As shown in fig 3, if the slope is below 3.5%, because of the acceleration caused by component

of the car weight, it can increase the speed. But the acceleration is little, so the speed increases slowly with the increased slope. If the slope is between 3.5% and 5%, because of driver enhances the consciousness of the slope, he begins to brake to decrease the speed. If the slope is above 5%, with the slope to be more and more steep and the driver’s vigilance and driving sensations to be much greater, so the driver takes long braking to make smoothly change of the speed. Moreover, the long braking generates "heat fade" phenomenon and driving fatigue, such as the phenomenon of legs fall asleep and others. Finally, that is prone to emerge traffic accidents.

As shown in fig 4, compared with the speed, if the slope is below 3.5%, the driver’s Heart Rate growth rate increases with the increased slope and speed, and when the slope i is about 3.5% Heart Rate growth rate is above 40%. If the slope is between 3.5% and 5%, the speed and Heart Rate growth rate all decrease with the braking, but Heart Rate growth rate is more than 30% yet. If the slope is above 5%, the driver cannot maintain vigilance and tension for long period, and the driver will be driving fatigue. However, though Heart Rate growth rate fluctuates smoothly, all the values are above 20% and some values are even above 30%.

It has been accepted that applying heart rate index on the effectiveness of driver’s fatigue and tension[6-7]. According to a great deal of literatures[8], when Heart Rate growth rate is above 20% the driver will be nervous, when the value is above 30% the driver will highly nervous, and when the value is above 40% the driver will be scared. Through the regression equation of the speed, Heart Rate growth rate with the slope, the paper gets a result that when the slope is about 3.5%, the speed and Heart Rate growth rate reach the maximum, and some values of Heart Rate growth rate are above 40%. When the slope is between 3.4% and 5%, the driver’s Heart Rate growth rate are all above 30%, at this moment, the driver has the biggest mental load and gets very tired. When the slope is above 5%, Heart Rate growth rate are all between 20% and 30%, that’s still high. Therefore, to sum up, the most nervous state is when the slope is 3.4%~5%, and combined with the speed curve, the speed is higher, so that is dangerous to driving and prone to traffic accidents.

The analysis of HRV is focused on the subtle time variation of the heartbeat cycle, it is different with the analysis of heart rate [9]. Particularly, using HRV to evaluate driving fatigue is very great [10]. Frequency domain analysis of HRV contains low frequency (LF) and high frequency (HF), LF

is regulated by the sympathetic nerve, and HF is mainly regu lated by the vagal nerve. And at the

state of fatigue and tension, the sympathetic nerve is more active. As shown in fig 6, obviously, LH is rising trend, while HF is falling down. This kind of changeable trend show that the driver’s sympathetic nerve keeps rising. In other words, the driver is very nervous and tired ,that’s greatly bad to the driving.

152 Current Development of Mechanical Engineering and Energy

Fig.7 Graph of the car speed changing with slope on long uphill

Fig.8 Tendency of heart rate growth rate changing with slope

0

10

20

30

40

50

60

70

80

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

time（s）

%

LF

HF

Fig.6 Graph of LF and HF changing with time

B. The long uphill highways

As shown in fig 7 and fig 8, under the highway condition of free stream, the changeable trend upon the slope with the mean speed and Heart Rate growth rate when driving on the long uphill highways.

0

10

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30

40

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60

0 1 2 3 4 5 6 7 8

slope(i/%)

t

h

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υ

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(

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)

)

0

5

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slope(i/%)

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)

Through the qualitative analysis of the data in fig 7, it shows that when driving on the long

downhill highways the slope i and the speed v is not simply linear relationship, because of the influences such as the acceleration, the component of car weight and the slope of highways. The paper gets the regression model about the speed and the slope by LabVIEW:

32 12.039.283.1179.29 iiiv +−+= (3)

Scope of application of the model: 0<i<8%. From the fig 3 and fig 7 show that: the changeable trends of the speed on long uphill and

downhill highways are approximately same. Based on the regression model about the speed with the slope on the long uphill highways, the paper acquires the maximum of the speed when the slope is also about 3.5%. If the slope is below 3.5%, the speed increases with the increased slope, because of the continual acceleration. If the slope is above 3.5%, for the steeper of the slope the shorter of the visual range, which results in judging the information of highways ahead is hard. In order to keep safety, the driver will slow the car down instinctively. Meanwhile, the speed begins to decrease with the increased slope and the particle gravity of the car.

The fig 8 shows when driving on the long uphill highways, the driver’s Heart Rate growth rate is little changed with the variations of slope. Though when the slope is about 3.5% the driver become very nervous and Heart Rate growth rate is large fluctuated and exceed 20%, Heart Rate growth rate is dropped and gets stable with the increased slope and the decreased speed. The pertinence coefficient of Heart Rate growth rate with the slope: R2=0.53<<1, which indicates the degree of fitting is low, so their correlation is very poor. Thus, generally during the long uphill highways the driver’s mental load will not add..

Conclusion

• Driving on the long downhill highways, the driver is much nervous and Heart Rate growth

rate is greatly fluctuated. If the slope is below 3.5%, Heart Rate growth rate will increase with the

increased slope and the increased speed, by this time, the driver’s psychological state is cautious. If

the slope is about 3.5%, Heart Rate growth rate excesses 40% and becomes the maximum. So this

moment the driver is most nervous, the concrete performances are greatly mental load, increased

feeling of fatigue and scare. In addition, now the speed is high, so it is prone to emerge traffic

accidents. If the slope is above 3.5%, Heart Rate growth rate are all above 20% and some values

excess 30%. Due to the continuous tension, the driver’s sympathetic nerve is more active, hence

Applied Mechanics and Materials Vols. 494-495 153

LF/HF increases. This time, driving fatigue is worse so that maybe result in mistake of driving, that

is deeply dangerous to the safe driving.

• Driving on the long uphill highways, the changing trend graph of the speed is similar to the

graph of long downhill highways, and the speed is low. The change of Heart Rate growth rate is

subtle, the pertinence coefficients of Heart Rate growth rate and the slope: R2=0.53<<1, which

indicates the degree of fitting is low. So the driver’s mental load is level and he keeps appropriately

prudent.

• Enhancing the administration of mountain highways. Importantly, the dimension of slope

should be suitable and the barrier inside of the highway should be dealt with. Because that can keep

good visual range. Especially, in the easily caused collapse and landslides highways, it is necessary

to found speed limit warning signs to ensure the driver’s safety.

Acknowledgment

The paper was supported by 2012 Key Projects of GuangXi education department (No.

201202ZD042).

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