Road Side Design: When is a Barrier Required?€¦ · Midwest Roadside Safety Facility Benefit/Cost Analysis •The estimated benefits to be derived from a specific course of action

Road Side Design: When is

a Barrier Required?

Jennifer Schmidt, Ph.D., P.E.

University of Nebraska-Lincoln

Midwest Roadside Safety Facility

Department of Civil Engineering

Guide Rail Safety Symposium

Brampton, ON

October 24, 2017


Midwest Roadside Safety Facility • Research organization located at University of

Nebraska-Lincoln

• Teaching students with research

• Started in the late 1980’s

• Clients State DOTs

FHWA

Private industry

Department of State

Motorsports organizations

Manitoba Infrastructure and Transportation


Research Capabilities

• Develop, test, evaluate roadside & motorsports safety hardware & features

• Component and full-scale vehicle crash tests

high-speed, large-mass, high-energy impacts

ISO 17025 certified laboratory

FHWA & European impact safety standards

DOS security barrier standards

• Non-linear finite element analysis

• Materials characterization & testing

• Implementation guidelines


MwRSF Facilities

Vehicle &

Fabrication

Shop

Outdoor

Proving Grounds

Materials &

Simulation

Laboratory


We are doing good in motorsports

• Prior to the SAFER

Barrier, an average

of 1.5 fatalities per

year

• Since the installation

of SAFER Barrier,

there have been no

fatalities due to

impacts with the

outer wall


SAFER Barrier

IRL-20 135.6 mph, 26.4 deg.

IRL-24 133.1 mph, 26.9 deg.

Up to 76% reduction in forces on the occupant


How about on the roadsides?

• Vehicle accident

fatalities in 2015

35,092 in US

1,858 in Canada

• Estimated cost

have reached well

over $50 billion

annually

iihs.org tc.gc.ca


Vehicle Fatalities in U.S.

iihs.org


Vehicle Casualties in Canada

tc.gc.ca


Vehicle Casualties in Canada

tc.gc.ca


Casualties in Canada

tc.gc.ca


Vehicle Crashes

• Approximately 56% of crashes are

Roadway Departure crashes in US

• Roadway Departure

Vehicle leaves traveled way

Crosses center line or edge line


Roadway Departure Crashes

safety.fhwa.dot.gov


Keep Vehicles on the Roadway

• Pavement Friction

• Rumble Strips

• Horizontal Curve Safety

• Nighttime Visibility

safety.fhwa.dot.gov


Provide for A Safe Recovery

• SafetyEdge

• Clear Zones

safety.fhwa.dot.gov


Reduce Crash Severity

• Ideally no vehicles would leave the

roadway or would be sufficient clear zones

completely free of hazards

• Vehicles continue to leave roadway

• Prevent vehicles from interacting with and

impacting hazards


Hazards are Everywhere














Types of Roadside Hazards

• Trees

• Utility Poles

• Steep Slopes

• Signs

• Drainage Features

• Lakes, Rivers, Oceans, Etc.

• Bridges

• Barriers

• Everything in a City


Just Remove All the Hazards!

• You can drive safely on or off the road



What to do with all the hazards?

• AASHTO Roadside Design Guide,

hazards on the roadside should be:

Removed

Redesigned to be safer

Relocated

Make it breakaway (and safer)

Shield it

Delineate it


Sometimes that means…

• Cutting down a tree that gets hit frequently

• Grading roadsides to make more

traversable slopes

• Designing and evaluating roadside safety

hardware to shield hazards


How to Decide If a Hazard Needs Treatment

• If the safety benefits from a specific safety

design or treatment equal or exceed the

additional costs for that treatment

• Benefit/Cost (B/C) Analysis

Example Program: RSAP (Roadside Safety

Analysis Program)


Benefit/Cost Analysis

• The estimated benefits to be derived from

a specific course of action are compared

to the costs of implementing that action

• Cost with barrier: installation cost,

maintenance cost, crash cost (may be

more frequent but lower severity)

• Cost without barrier: crash cost (typically

higher severity)

AASHTO RDG


Benefit/Cost Analysis

• Factors:

Design speed

Traffic volume

• Evaluate options:

Remove or reduce the area of concern so no

shielding would be required

Install an appropriate barrier

Leave the area of concern unshielded

AASHTO RDG


Roadside Trees

tentree.com


Trees - Background

• Naturally occurring roadside fixed objects

• 8% all traffic-related fatal crashes (FARS

1999-2009)

• 90% tree impact fatalities located on 2-

lane roadways (FARS 1999-2009)

• 30% fatalities occur on low-volume roads

(FARS 1999-2009)

• 26% fixed-object fatal crashes (FARS

2009)


Tree Treatment

AASHTO RDG


Tree Treatments

• Pavement marking

• Rumble strips

• Signs

• Delineators

• Roadway improvements

• Tree removal

• Shielding

AASHTO RDG


Low Volume Roads

• Simulated

“Do nothing” – baseline

Tree removal

Install longitudinal barrier

• Other Options

Delineation

Edge treatments


Install Longitudinal Barrier

• High installation costs

$18.16/lf plus terminal

$45/lf plus terminal

• Viable situations

Very long sections of close spaced trees

Difficult tree removal

Regular new tree growth

• Scenarios evaluated not cost effective


Tree Removal, B/C = 4

ADT No. of Trees

1 2-10 11-25 >25

0-99

100-199

200-299

300-399

400-500

Tree Diameter, Spacing, and Offset Dependent

Remove Tree(s)


Example: Georgia DOT


Killer Trees

Urban Non-Collision

Fatal Tree Fall

Great Falls, VA in 2012


Utility Pole Treatment

AASHTO RDG


Breakaway Luminaire Poles

AASHTO RDG


Breakaway Signs


Breakaway Sign Supports


Overhead Sign Structures

• May need a barrier if located in clear zone


Offset From Hazard

• Based on dynamic deflection from barrier

testing

• Varies for different barriers

AASHTO RDG


Foreslope Configurations

• Recoverable: 1V:4H or flatter

• Non-recoverable: 1V:3H to 1V:4H

• Critical: steeper than 1V:3H

AASHTO RDG


Midwest Guardrail System - M30 Guide Rail


Note

• Not all barriers are meant to be placed on

the slope or at the slope break point

AASHTO RDG


AASHTO RDG


AASHTO RDG


Drainage Features


Culvert Grate


Bridge Rails


Bridge Rails


MASH Barrier Test Levels Test

Level Test Vehicle

Vehicle

Weight (kg) Speed (km/h)

Angle

(degrees)

1 1100C Small Car

2270P Pickup Truck

1,100

2,270

50

50

25

25

2 1100C Small Car

2270P Pickup Truck

1,100

2,270

70

70

25

25

3 1100C Small Car

2270P Pickup Truck

1,100

2,270

100

100

25

25

4

1100C Small Car

2270P Pickup Truck

10000S Single-Unit Truck

1,100

2,270

10,000

100

100

90

25

25

15

5

1100C Small Car

2270P Pickup Truck

36000V Tractor-Van Trailer

1,100

2,270

36,000

100

100

80

25

25

15

6

1100C Small Car

2270P Pickup Truck

36000T Tractor-Tank Trailer

1,100

2,270

36,000

100

100

80

25

25

15


Barrier Selection Test Level

• All test levels developed to contain

passenger cars and pickup trucks

• Select test level based on roadway speed

and ADT

• Higher performance levels (TL-4, TL-5,

TL-6) may be selected:

High percent average daily truck traffic

Adverse geometrics

Severe consequences of penetration into

opposing lanes AASHTO RDG


Barrier Selection

• Low volume, low commercial vehicle

Cable or box beams system

• High volume with large number of trucks

Steel beam or concrete barrier

• High volume with very large number of

trucks in critical areas

High performance barrier

RSM


Bridge Rails & Concrete Barriers

• End of bridge rail or concrete barrier can

be hazardous if not shielded appropriately


Sloping the end…not so good


Transition Adjacent to Rigid Barrier


Transition to Rigid Barrier


Summary

• Installing barriers is not always the best

solution when hazards are near roadway

Barrier itself is a hazard (but a safer one)

A few fatalities occur with barrier impacts

• Appropriate barriers do save lives

• Limited funds exist for installing barriers

Need to prioritize locations

Accident history

Benefit/cost analysis


QUESTIONS? Jennifer Schmidt

(402)-472-0870

[email protected]

mwrsf.unl.edu

Documents

Road Side Design: When is a Barrier Required?€¦ · Midwest Roadside Safety Facility Benefit/Cost Analysis •The estimated benefits to be derived from a specific course of action