SJ-5112_1011_4 Safety Issues on Geometric Design

8/7/2019 SJ-5112_1011_4 Safety Issues on Geometric Design

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SJ-5112 Perancangan Geometrik Jalan

Safety Issues on Geometric Design Sony S Wibowo, Ph.D


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Special Notes on Road Safety problems

o

Accidents on horizontal curves are a cause for concern inall countries, whatever the level of development of theirroad system

A recent study has found that in Denmark, about 20% of all

personal injury accidents and 13% of all fatal accidents occur oncurves in rural areas (Herrstedt and Greibe, 2001).

In France, over 20% of fatal accidents occur on dangerouscurves in rural areas (Herrstedt and Greibe, 2001).

o Accidents on bends are undoubtedly a major problem inmany developing countries, although the proportion ofsuch accidents is dependent upon both the topography

and demography of each country


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o

Accidents on horizontal curves tend to be of two main types: Running off the road and hitting an object

Lost control and Rolled over

o There can also be a significant number of Head On andSideswipe accidents at higher traffic volumes.

o The apparent cause of these accidents is usually the driver

entering the bend at too high a speed; and the reason for thiscan be because :

The driver was willfully travelling at a high speed

Paying insufficient attention He or she misjudged the severity of the bend


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o Such misjudgements can be caused of the bends visual configuration

poor delineation (marking out)

because it was unexpectedly sharp after a series of gentlecurves or after a long straight (tangent) section

o Another major problem can occur when driverssometimes ignore the no-overtaking enforcement.


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o

When travelling around bends, the higher forces put on the road surface by the side thrust of the tire

frequently cause the surface aggregate on bends to polish morequickly than the rest of the road,

it is aggravating the problem of safety

o There can also be underlying problems in the geometricdesign of the curve

because the basic assumptions are not applicable to the design

e.g. a high proportion of drivers exceed the design speed

o On gravel roads in particular, the loss of super-elevation inthe cross-sectional profile through lack of maintenance may

result in the effects of a horizontal curve being more severethan as designed


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Special Notes on Road Safety solutions

o For all bends below the desirable minimum standards,

warning signs should be provided to give the driver an idea of how severe thebend is

this should ideally follow a standard whereby the most dangerous bends have thehighest level of signing and road marking

o The road alignment should be designed to provide a uniform road layouttraversable with clear forward visibility.

o If head-on accidents are a problem

double white lines should be enhanced with a physical device appropriate to theroad conditions

ranging from line markings that induce vibrations to heavy duty road studs or rubber posts.

o Use higher skid resistance materials on critical bends particularly in wetenvironments.

o Curve widening should be applied to the inside edge of the curve


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Special Notes on Road Safety


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Special Notes on Road SafetyIn many countries where line markings are ignored, more physicaldeterrents to crossing the centre line required.


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Gabions and Barriers on Dangerous Bends


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Gabions and Barriers on Dangerous Bends


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In Urban Area


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end of this section

SJ-5112_1011_4 Safety Issues on Geometric Design

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