road design - environmental science & · pdf filefrom fhwa and state dots, also from...

Road Design

Susan Handy TTP Orientation Seminar

October 2012

Level Agencies Primary concern

Primary role

Federal FHWA FTA

National Highway System

Funding Policy

State DOT Highways outside metro areas

Planning Building Operating

Regional MPO Transit

Highways, transit within metro areas

Planning

Local Planning Public Works

Local streets

Planning Building Operating

Road Design in the U.S.

Manuals and Guidelines from FHWA and state DOTs, also from… AASHTO – American

Association of State Highway and Transportation Officials

ITE – Institute of Transportation Engineers

TRB – Transportation Research Board

Topics

• Network design • Facility design • Plus others

Network Design

• What are the two main purposes of streets/roads/highways?

• What’s the main difference between streets vs. roads vs. highways?

National Committee on Urban Transportation, 1958

City of Sunnyvale, 1957

ITE Street Layout Principles, 1984

City of Austin, Comprehensive Plan, 1994

Benefits of grid…?

• More direct routes – Less distance

• Less driving (?) – Less pollution, energy consumption, noise, etc.

• More walking/biking – More exercise, less weight, better health, etc.

– Better efficiency • Emergency response time • City services

Connectivity Measures

Source: Handy, Paterson, and Butler 2003

Source: Handy, Paterson, and Butler 2003

Source: http://www.fotosearch.com/photos-images/cul-de-sac.html

Berkeley Diverters

Source: http://www.ci.berkeley.ca.us/transportation/Bicycling/BB/BicycleBoulevardTreatments.html

Village Homes, Davis

Source: Google Maps

Davis Greenbelt System

Source: Google Maps

Houten, Netherlands

Source: Google Maps

Facility Design Responsibility Influence

Local Streets Cities and counties

ITE – Institute of Transportation Engineers

Highways and Freeways

State DOTs AASHTO – American Association of State Highway Officials

http://www.ite.org/bookstore/RP-011C.pdf

http://www.ite.org/bookstore/RP-011C.pdf

http://www.ite.org/bookstore/RP-011C.pdf

Source: http://www.ashland.or.us/Files/street%20standards_001.pdf

Source: http://www.ashland.or.us/Files/street%20standards_001.pdf

Source: http://www.ashland.or.us/Files/street%20standards_001.pdf

Innovations/Trends

• Traffic Calming • Skinny Streets • Road Diets • Complete Streets • Green Streets • Context-Sensitive Design • Others…

Traffic Calming

"Traffic calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior and improve conditions for non-motorized street users." - ITE Subcommittee on Traffic Calming

Speed Control Measures

Vertical Deflection Horizontal Deflection Horizontal Narrowing Other Measures

Speed Humps Traffic Circles Neckdowns Examples

Speed Tables Roundabouts Center Island Narrowings

Raised Crosswalks Chicanes Chockers

Raised Intersections Realigned Intersections

Textured Pavements

Speed Lumps *

Speed Cushion *

Split Speed Hump *

Volume Control Measures

Divertive, Restrictive Other Measures

Full Closures Examples

Half Closures

Diagonal Diverters

Lateral Shift *

Median Barriers

http://www.trafficcalming.org/measures2.html

Traffic Circles Roundabouts

http://www.trafficcalming.org/measures2.html

http://www.trafficcalming.org/measures2.html

Chicanes Neckdowns

Narrow Street Scenarios

http://darkwing.uoregon.edu/~cpw/projects/pdf/featured/tgm_2003/powerpoints/285,13,Narrow Street Scenarios

Narrow Streets

Canyon Rim Village, Medford

http://darkwing.uoregon.edu/~cpw/projects/pdf/featured/tgm_2003/powerpoints/366,11,Narrow Streets

Road Diet

Fifth Street Road Diet in Davis: Coming Summer 2013

Complete Streets

http://la.streetsblog.org/wp-content/uploads/2008/10_06/10_8_08_complete_streets.jpg

Marcy McInelly, SERA/Urbsworks

Green Streets

https://bookstore.transportation.org/item_details.aspx?ID=110

“Context-Sensitive Design”

Source: http://www.dot.ca.gov/hq/oppd/context/main-streets-flexibility-in-design.pdf

Riverfront Parkway and Downtown Streets, Chattanooga, TN

Image: City of Chattanooga and River City Company

Riverfront Parkway, Chattanooga, TN

“Before” Conditions

Image: City of Chattanooga and River City Company

Image: City of Chattanooga

Reconstructed Riverfront Parkway

Road Design Conundrum

Crash risks minimized but high speeds

Crash risks remain but low speeds

Parking

Parking Problems

• Minimum parking requirements for residential and commercial development, in zoning codes – Excess parking

• Free curbside parking in central business districts – Excess driving – “cruising” to find spaces

Parking Requirements

“Free parking isn't really free. In fact, the average parking space costs more than the average car. Initially, developers pay for the required parking, but soon tenants do, and then their customers, and so on, until the cost of parking has diffused throughout the economy. When we shop, eat in a restaurant, or see a movie, we pay for parking indirectly because its cost is included in the price of everything from hamburgers to housing. The total subsidy for parking is staggering, about the size of the Medicare or national defense budgets. But free parking has other costs: It distorts transportation choices, warps urban form, and degrades the environment.”

Source: http://www.planning.org/bookservice/highcost.htm

Traffic Management

• Approaches: – Traffic control devices to

regulate behavior – Roadway design to shape

behavior

• Goals: – Safety – Efficiency – Plus livability!

Source: http://mutcd.fhwa.dot.gov/pdfs/2003r1/pdf-index.htm

MUTCD Principles

• Purpose is “… to promote highway safety and efficiency by providing for the orderly movement of all road users… throughout the Nation…”

• “The decision to use a particular device at a particular location should be made on the basis of either an engineering study or engineering judgment…”

• Not a legal requirement • Not a substitute for engineering judgment

Speed Limits

• MUTCD section 2B-10 (update: 2B-13) requires that the numeric value be determined on basis of an engineering study. The following factors should be considered: 1. Road surface characteristics, shoulder condition, grade, alignment and

sight distance. 2. The 85-percentile speed and pace speed. 3. Roadside development and culture, and roadside friction. 4. Safe speed for curves or hazardous locations within the zone. 5. Parking practices and pedestrian activity. 6. Reported accident experience for a recent 12-month period.

For a discussion, see: http://www.motorists.org/speed-limits/safety-setting-limits

Level of Service TRB’s Highway Capacity Manual

LOS = f (volume/capacity) How to increase LOS?

Result: Massive Intersections

Next up: Pavements!