1.39k likes | 1.5k Views
Complete Streets: Basic Design Considerations. John N. LaPlante, P.E., P.T.O.E. T.Y. Lin International Prepared for the: Annual Meeting of the AASHTO Highways Subcommittee on Design July 15, 2008. What is a Complete Street?.
E N D
Complete Streets: Basic Design Considerations John N. LaPlante, P.E., P.T.O.E. T.Y. Lin International Prepared for the: Annual Meeting of the AASHTO Highways Subcommittee on Design July 15, 2008
What is a Complete Street? A Complete Street is safe, comfortable and convenient for travel via automobile, foot, bicycle, and transit.
An incomplete street: Too narrow for comfortable 'sharing'
An incomplete street: Uninviting for transit riders
An incomplete street: Room for vehicles, but no room for people
AASHTO Ped Guide • AASHTO Ped Guide published in October 2004. • Included many new and innovative concepts. • Reiterated some often overlooked AASHTO Green Book guidelines.
Current Green Book AASHTO Green Book encourages roadway designers to provide for peds. “Interactions of pedestrians with traffic are a major consideration in highway planning and design.”
AASHTO Ped Guide Safety is a key consideration. Peds are the most vulnerable of all roadway users.
AASHTO Ped Guide Accessibility is also key. Ped facilities should accommodate peds of all abilities.
Basic Design Elements • Sidewalks • Crossing the street • Medians and islands • Traffic signals • Crosswalks • Crosswalk markings • Curb extensions • Transit • Bicycles
AASHTO Ped Guide Sidewalk Design Not after space for future sidewalks is all gone
AASHTO Ped Guide Sidewalk Design “All roadways along which pedestrians are not prohibited should include an area where occasional pedestrians can safely walk.” • Unpaved walkway • Shoulders in rural areas • Sidewalks in urban areas Locations with no sidewalks are twice as likely to have vehicle-pedestrian crashes than sites with sidewalks.
Pedestrians can get by without sidewalks on quiet streets Ashland OR
Shoulders serve pedestrians in rural areas Benton County OR
At a certain point, sidewalks are needed Canyonville OR
“Goat trail” indicates sidewalks are needed Jefferson Parish
AASHTO Ped Guide Sidewalk Design Set triggers for future sidewalks • Development densities • Developer requirements • Going from open to closed drainage
The AASHTO “Green Book” states: “Sidewalks are integral parts of city streets” Sidewalks are not added to streets, they are part of the street
Sidewalks should not end midblock Forcing pedestrian into street Fredericksburg VA
AASHTO Ped Guide Sidewalk Design Sidewalks on only one side of the street? • Generally not recommended • Lacks connectivity • Weakens pedestrian safety by requiring unnecessary street crossings
Mountable curbs are not appropriate on local streets Casper WY
Separated sidewalk is uncluttered, pleasant to walk on Reno NV
Parkway separation makes it easy to meet ADA at driveways Salem OR
Narrow curbside sidewalks are inadequate in commercial areas Reno NV
Pedestrians want & need to cross the street safely Pedestrians shouldn’t be terrified crossing the street Santa Ana CA
Speed Matters High speeds lead to greater chance of serious injury & death
First scenario: Speed 25 MPH 100’ = distance covered in 2.5 sec. perception/reaction time Driver applies brakes 100’ 150’
First scenario: Speed 25 MPH Driver applies brakes 50’ stopping distance (wet pavement) 100’ 50’ 150’
First scenario: Speed 25 MPH Result: Nothing happens beyond one scared child, driver & parent! 100’ 50’ 150’
Second scenario: Speed 38MPH 140’ = distance covered in 2.5 sec. perception/reaction time Driver applies brakes 140’ 150’
Second scenario: Speed 38MPH Driver applies brakes 140’ 150’
Second scenario: Speed 38MPH In the last 10’ car slows to 36 MPH 140’ 150’
Second scenario: Speed 38MPH Result: a high speed crash 150’
Second scenario: Crash speed 36 MPH First scenario: no crash Where do these two scenarios lie on the pedestrian fatality risk scale?
Complete Streets Design Controls • Conventional design criteria primarily based on: Functional class Design Speed • Complete Streets design begins with Target Speed: • Desirable operating speed • Mobility for motor vehicles • Safety for pedestrians and bicyclists • Usually posted speed limit
Defining Mobility • Typical experience: • 45 mph speed • 2 min wait at signal
Defining Mobility • Viable alternative: • 2-way progression set for 30 mph
Benefit/Cost Analysis • Reducing speed from 45 mph to 30 mph • For a 5-mile trip, a 3.33-minute delay • Assume 30,000 ADT and $20/hr driver cost • $12.154 million in loss to economy, right? • Wrong! • Delay for each person is still 3.33 minutes • Less time than their daily stop for Starbucks • Community benefit • Slower operating speeds • Safer and more comfortable ped crossings
Roadway Capacity Analysis • Design urban roadways to LOS D • Designing to LOS C for peak hour means: • Unnecessary pavement, waste of tax dollars • Increased ped crossing times, thus reducing vehicular movement times • Increased operating speeds for other 22 hours
Medians and Islands Reduce crashes by 40%
Basic Principle Break long complex crossing into two simpler crossings
Poor sign placement Choosing location for island: must have O & D Corvallis OR
In this case, apartments across from bus stop and stores Corvallis OR