Vegetation Control For Safety

Russ Johnson – Maintenance Supervisor - WSDOT

Don Petersen – Safety/Design Engineer - FHWA

Overview

Introduction Specific Items to Check

Sign Visibility Clear Sight Lines Drainage Side Road Visibility Roadside Trees Pedestrian Paths

Overview (continued)

Keeping Traffic Control Devices Visible Stopping Sight Distance on Curves Intersection Sight Distance Mowing for Safety Resources on Vegetation Control for

Safety

Introduction

1. Scope and Objectives 2. Goals of Vegetation control3. Roadside Vegetation Management

Scope and Objectives

1. Safety is a main concern2. One potential hazard is vegetation3. The purpose of this presentation

Vegetation Control Goals

1. Keeping Signs visible to drivers2. Keeping road users visible to drivers

1. Other vehicles2. Bicycles3. Pedestrians

3. Improving visibility of livestock and wildlife4. Improving pedestrians and bicyclists see vehicles5. Keeping sidewalks and paths clear and free

Vegetation Control Goals

6. Removing trees close to roadway7. Helping drainage systems function8. Preserving pavements9. Controlling noxious weeds

Roadside Vegetation Management

Specific Items to Check

Sign visibility1. Visible to drivers at all times2. Look for braches and brush that

block signs and other control devices

3. Signs that control right-of-way are most critical (stop and yield signs)

Specific Items to Check

Clear Sight Lines1. Tall grass and brush in the shoulder,

ditch and backslope can obscure:1. Culvert Headwalls2. Drainage inlets3. Guardrail end4. Object markers5. Livestock and wildlife

Drainage

Weeds, turf and sod can interfere with drainage:

1. Creates a secondary ditch2. Pavement problems3. Ponding on pavements causing

hydroplaning or areas prone to icing

Side Road Visibility

Roadway intersections increase the potential for crashes

1. Mainline drivers need to see entering vehicles2. Entering drivers need to see mainline vehicles

Roadside Trees

One of the most common cause of fatal and serious injury crashes

Clearzone Adjacent to roadway Clear of fixed objects

Trees larger than 4 inches The closer to the roadway

Pedestrian Paths

Increased emphasis on walking for exercise and transportation

Importance of pedestrian safety and accessibility Free of overhanging or protruding

vegetation Tripping hazards caused by sidwalk

displacement

Sidewalk Corridor Zones

Furniture Zone

Pedestrian Zone

Frontage Zone

Keeping Traffic Control Devices Visible

Unobstructed line of sight to roadside signs or hazards

Far enough ahead to allow safe reaction time

Stopping Sight Distance (SSD) on Curves

Vegetation on the inside of curves restrict the drivers line of sight Cut weeds, brush, or trees for

adequate stopping sight distance Sight distance is the distance

necessary to notice a problem, realize a stop is necessary, and to come to a complete stop

SSD on Curves

SSD is important on all roads Sight distance is measured along

the travel path of the vehicle The following slide illustrates how

to determine SSD

Intersection Sight Distance

A clear line of sight along crossroad

Early enough to see1. Conflicting vehicles2. Bicyclists3. Pedestrians

Mowing for Safety

Three types of mowing1. Safety mowing2. Transition Mowing3. Selective mowing

Resources

A Policy on Geometric Design of Highways and Streets, 2004

“Integrated Roadside Vegetation Management”, NCHRP Synthesis 341

Manual on Uniform Traffic Control Devices, 2003 Volume 3: A Guide for Addressing Collisions with

Trees in Hazardous Locations, NCHRP Report 500 FHWA Roadside Vegetation Management

http://www.fhwa.dot.gov/environment/index.htm

National Roadside Vegetation Management Associationwww.nrvma.org

Questions?

JOHNSRA@wsdot.wa.gov - 509-324-6589

Don.Petersen@fhwa.dot.gov - (360)534-9323