Transportation Plan - 2009, amended

6.4 Intersection Design Guidance

Figure 6.12 (A)

Intersections at roadways deserve special treatment and consideration in the planning and design processes for several reasons: • Intersections are where the majority of conflicts between cars, pedestrians, and cyclists occur; • Intersections mark transition zones between one type of road- way and another, often with each road having different capac- ity and speed characteristics; and • Intersections are the places where the highest land values and most space are typically provided, often generating higher in- tensity developments than typically occur mid-block.

Figure 6.12 (B) illustrates some common design considerations. A. Ensure that all intersections have ADA curb ramps designed to NCDOT and national specifications, and that other features like light poles (shown here with a required pedestrian countdown signal head) allow for easy movement of wheelchair users. B. Wayfinding signage should be consistent, and consistently located to ensure high visibility. Again, allowing for at least 40” of clear space around the sign is desirable, as are viewing characteristics that support ADA populations. C. Similarly, water fountains like the one shown here should allow maneuverability without sacrificing accessibility. D. Waste receptacles should be conveniently-placed, highly visible, and emptied frequently. E. The curb extension shown here is desirable in downtown locations to help reduce pedestrian crossing distances, provide a more secure parking area behind the extension, and slow traffic turning speeds. Streets and intersections can be broken down into five categories, as shown in Figure 6.12 (A). The street zone is everything between the curb lines; but what happens in the other four zones leading into the built up area is equally as important to ensure compatibility between street and development design. The width of each area depends on the intensity of the land use and the amount of available right-of-way and setbacks from buildings. Narrower setbacks may be desirable in lower speed ar- eas to help create the feeling of an enclosed space to slow traffic and create a more walkable community. In such cases, the Streetscape and Amenity Zones are often one and the same, and the door zone becomes narrow with special attention paid to entranceways and window-driven retail opportunities.

Figure 6.12 (B)

Figure 6.12 (C)

Typical Cost

Intersection Treatments and Amenities

Cost Unit

Basic Infrastructure Sidewalks

$53 linear foot $27 linear foot

Curbing

Signal Mast Arm with Signal*

$150,000

each each each each each

Signal Mast Arm (Double) with 2 Signals* $175,000

Strand (Wire) Signal Pole with Signal*

$80,000 $1,900

Basic costs for intersection treatments are indicated in Figure 6.12 (C). The actual cost will vary somewhat depending on the size (number and width of lanes) as well as the traffic control devices already in place. Crossing width is used to de- termine whether to use a mast arm rather than a strand wire signal. Up to 70 feet is a reasonable length for a mast arm; longer crossings are permissible, up to 84 feet, but the width of the base, foundation and other materials increase. Three to four feet at the tip of the mast arm is reserved for a sign, and about 16 feet at the pole end is needed to clear the sidewalk and buffer. This translates into a functional crossing width of about 48 feet, or four lanes of traffic. Because intersections are such highly visible locations, they get noticed much more than other parts of the street. Therefore, textured / colored pavement treatments, wayfinding signage, and quality amenities like furniture and pedes- trian-scale lighting features tend to have superior cost-benefit characteristics. The design criteria in Figure 6.12 (D), adapted from the NCDOT Traditional Neigh- borhood Design Manual, may be adjusted according to NCDOT standard poli- cies on state-maintained streets inside of Morrisville. These criteria fit pedestrian- oriented areas; higher design values may be required on higher-speed streets with little pedestrian and bicycle activity.

Pedestrian Signal

Sign and Post

$250

$500 - $1,000 $1,200

Wayfinding Sign

each

ADA Ramp

each

Amenities Bike Racks (Inverted 'U', 2 bicycles) Crosswalk (Tape, Transverse Lines)

$700 $100 $300

each each each each

Crosswalk (Tape, Ladder)

Crosswalk (Textured Concrete)

$20,000 $10,000- $40,000

Refuge Island

each

each corner

Curb Extension

$10,000

Raised Crosswalk (Speed Table)

$2,500 $2,000

each

Speed Hump each *Note: Does not include site-specific cost of installation, e.g., electrical and wiring, foundations.

Street Intersection Figure 6.12 (D)

Land Use

Posted Speed Curb Radius Planting Strip Sidewalks

Bike Treatment

Alley

Commercial

<20mph 25mph

15' 15'

0' - 3'

None

None

Local - Residential

Low-Density Residential

3'

5' one side Wide Outside Lane

Local - Activity Center Mixed Residential-Commercial

15-25mph 25-35mph

15'-20' 20'-25'

6' or greater 8' two sides Wide Outside Lane or Sharrows

Collector

Mixed Residential-Commercial

5' Min. 8' Min. 8' Min.

5' two sides Wide Outside Lane or Sharrows

Minor Arterial Major Arterial

Medium Density Res.-Commercial 35-45mph

25'

5' two sides 4' - 6' Bicycle Lane 5' two sides 6' Bicycle Lane

Commercial

35-55mph

25' +

48

6 Design Guidance