2. Mark Bloschock - How Barriers Work.pdf

7/26/2019 2. Mark Bloschock - How Barriers Work.pdf

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Mark J. Bloschock P.E.

Austin, Texas

[email protected]


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76% in the Vulnerable Users Group!


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Different and smaller cars


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Motorcycles an Lane Filtering


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Pedestrians Share the Roads Everywhere


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Pedestrians Walking Facing Traffic


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TALLER DE SEGURIDAD VIALBogot, Colombia02-03 Marzo

Better Roads. Better World.

Greg Speier


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TALLER DE SEGURIDAD VIAL

Bogot, Colombia02-03 Marzo

Better Roads. Better World.

Choosing the Appropriate

Barrier System toContain Errant Vehicles


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Outline

What does a roadside barrier do and why do we need

barriers?

Test levels

Classification of roadside barriers

How each class works

Basics of transitions and connections

Basics of terminals Barriers and the clear zone

Anchor bolts


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What does a roadside barrier do?

Contain an errant vehicle

Re-direct the vehicle

Minimize the effect on driver and passengers

Maintain the stability of the vehicle .


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How longitudinal barriers work

1 minute


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Contain and re-direct

35 seconds


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30%

23%19%

7%

5%

5%4%

7%

Roadway Departure Crashes

Overturn 30 Opposing Direction 23

Trees shrubs 19 Signs, Poles, Signals 7

Other fixed 5 Barriers 5

Topography 4 Other 7

Source: FHWA web site July 2015

Why do we want to contain and re-direct?


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Not to scale


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Two important terms

Dynamic deflection - Maximum deflection of the traffic

face of a barrier during an impact

Working width - Maximum distance between thetraffic face of the barrier and the maximum

deformation of the barriers main components or of

the vehicle during the impact .


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D = Dynamic deflection

W = Working width

D = Dynamicdeflection

W = Workingwidth


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Test levels


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MASH test levels NCHRP 350

820C2000P

820C2000P

820C2000P

820C2000P8000S

820C2000P

36000V

820C2000P

36000T

20

20

20

20

20

20


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Classification of roadsidebarriers


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Classification

of

longitudinal

barriers by

deflection

and post

type

Flexible barrier

with collapsible

posts:

Deflection1 5 m

Semi-rigid

strong post:deflection

0.3 2 m

Rigid:

Deflection

0 0.6 m


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Classification of longitudinal

barriers by deflection and post type

Flexible barriers with collapsible posts

Cables

W-beam or thrie-beam

Steel plates with wood trim

Conventional semi-rigid barriers

Rigid barriers


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How each class works


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D


W = Working width


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D

W


W = Working width


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D

WD = Dynamic deflection

W = Working width


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Basics of transitions andconnections


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Situations that require a transition

Crash cushion to steel barrier (or concrete wall) when

2 way traffic W-beam to thrie-beam .

N C ti B t B id R il d G d il


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No Connection Between Bridge Rail and Guardrail


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No Transition!


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No Transition!


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Bolted Connection


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Basics of terminals


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Standing Guardrail End


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Wh d i l d ?


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What does a terminal do?

Contain an errant vehicle

Re-direct the vehicle

Minimize the effect on driver and passengers

Maintain the stability of the vehicle .


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Function of a terminal

Anchor the barrier

Without

Presenting a spearing risk

Causing the vehicle to become airborne Causing the vehicle to flip over .


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58 of 47Taller de Seguridad Vial - Lima, Per - 12-13 Noviembre

Trailing End Treatments


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8 posts - full space - no cable

5 seconds


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8 posts - half space - cable

5 seconds


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8 posts - half space - no cable

5 seconds


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8 posts - full space - no cable - 4th post

5 seconds


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8 posts - half space - no cable - 4th post

5 seconds


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Barriers and theClear Zone

T

he clear zone


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The clear zone

The unobstructed, traversable area provided beyond

the edge of the through traveled way for the recoveryof errant vehicles.

The clear zone include shoulders, bike lanes, and

auxiliary lanes, except those auxiliary lanes that

function like through lanes.

Source: Roadside Design Guide 4th

Edition

The clear zone


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The clear zone

Clear zone is a function of:

Speed Traffic

Slopes

Curves .


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Breakaway sign bases?


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Breakaway sign bases?

Clear zone


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Clear zone

RDG guidance is a goal that often can not be obtained

Most errant vehicles are under control in a relatively smallarea

Many agencies strive to obtain a 10 m wide clear zone

When a terminal is placed at the start of a barrier many

agencies shoot for a run-out that is 20 m long.

Where do we start a barrier?


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70 of 47Taller de Seguridad Vial - Lima, Per - 12-13 Noviembre

Where do we start a barrier?

A barrier should begin at the point where an errant vehicle at a

typical departure angle (15 - 25) would no longer be able to

stop by itself before exiting the available clear zone

This is the Beginning of the Length of Need (BLON)

In the case of gating terminals the gating part of the barrier

should be positioned before the BLON.

Source: RDG 2011Departure angle

Run out length


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Source: RDG 2011

Suggested run-out lengths


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30ft(9m)75 ft (22.5 m)

Clear Zone Run-out

Not to scale

Run out length

Good clear zone example


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Good clear zone example


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TALLER DE SEGURIDAD VIAL

Bogot, Colombia02-03 MarzoBetter Roads. Better World.

Anchor bolts(Epoxy Adhesive Anchor Bolt Systems)


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Drill to

design depth

Blow out Brush w

alcohol

Brush

again

Blow out Epoxy

1/3

Screw bolt

Dont push

Torque nut

After hardened


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2 b 2 b 2


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2 by 2 by 2

2 b 2 b 2


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2 by 2 by 2

2 times with the air nozzle in each hole

2 b 2 b 2


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2 by 2 by 2


2 times in and out with the brush

2 b 2 b 2


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2 by 2 by 2


2 times in and out with the brush

2 times with the air nozzle in each hole again


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Session review


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Session review

What does a roadside barrier do?

Test levels

Classification of roadside barriers

How each class works Basics of transitions and connections

Basics of terminals

Barriers and the clear zone

Anchor Bolts

Documents

2. Mark Bloschock - How Barriers Work.pdf