Chapter 5

WHAT IS THE FRAMEWORK OF COMMUNITY?

TECHNICAL CONSIDERATIONS & PEDESTRIAN CIRCULATION

REPORTER: ERELYN MAE ROSELLE C. NAQUILA

Technical considerations

•Streets are usually crowned in the center for positive drainage and may utilize a curb and gutter system to channel surface runoff to an outfall and to act as a visual and physical barrier between vehicular and pedestrian spaces.

• Curbing is usually 6 inches high, although a 4-inch rolled curb is sometimes used. Grassed swales and shoulders can be found in areas with low-density development.

• Pavement width varies; however, 24 to 30 feet from curb to curb is common for a 50-foot right-of-way.

• A right-of-way of this width usually allows parking on one side of the street, and a 60-foot right-of-way allows parking on both sides of the street.

• Streets are laid out using a system of horizontal and vertical curves. Depending on the right-of-way width and design speed of the road, the minimum centerline radius of a horizontal curve can vary from 75 feet for a 50-foot right-of-way to 250 feet for some state-maintained highways.

• Vertical curves provide positive drainage and enable the designer to adapt a road to topographic conditions.

• Broken-back curves and reverse curves are usually designed with at least a 100-foot tangent or straightaway between them to allow recovery time for the motorist and additional braking space.

Intersections

•Intersections should intersect at right angles.

•It is considered unsafe, however, to

design an intersection with less than 30 degrees of

deflection.

•Also, intersections should be either directly opposite to one another or at least 125 feet apart from centerline to centerline.

INTERSECTIONS

• The curved section connecting two streets or street returns at intersections should not be greater than 10 to 15 feet for most residential streets as measured on the right-of-way.

• A 10-foot radius equals a 20-foot curb radius. Why? This ensures that motorists are forced to stop when required and makes the crossing distance for pedestrians as direct and short as possible.

Cul-de-Sacs• These are usually required for school buses, fire trucks, and

garbage trucks, but should actually be considered on a case-by-case basis to allow flexibility and interest in the land plan.

• In TNDs, cul-de-sacs are rarely used because they prevent connectivity.

• If cul-de-sacs must be used, pedestrian and bicycle access should be provided through the dead end of the street to allow connections to the neighborhood street beyond.

• In CSDs, cul-de-sac lengths vary, but generally should not exceed 1000 feet in length. The right-of-way dedication of cul-de-sac bulbs or turnarounds is usually required to be 100 feet in diameter with an 80-foot curb diameter.

Cul-de-Sacs

• The amount of traffic must be considered when designing a road network in the community.

• Most intersections of minor residential streets don’t require turn lanes, but larger intersections serving employment or retail centers do, especially those accessed by divided roadways.

• A good rule of thumb for minimum requirements for these turning lanes is 150-foot vehicle stacking with 150 feet of transition space. This may require additional right-of-way dedication along a property frontage.

Trumpet Intersections

•are an at-grade solution, allowing some traffic to continue to move even when through traffic is stopped by traffic signals.

•They can also aid in creating a sense of place by providing space for entrance icons, landscaping, and water features.

Trumpet Intersections

Rotary• Rotaries, like trumpets, are good place makers.

• They allow single-way movement around a center island (a focal point) and do not require signalization at lower traffic counts.

• Useful for intersections of 500 to 1000 trips per hour.

• Work well in residential areas, especially if the center area becomes a landscaped park.

Rotary Intersection

Pedestrian Circulation

• Walking is not only the best form of exercise, but it’s the best way to meet our neighbors. Meeting our neighbors makes for better community. It’s more than providing a sidewalk along every street.

• PROBLEMS TO PEDESTRIAN CIRCULATION

• Most of what we call pedestrian ways are sterile and inhospitable environments, especially those located along busy thoroughfares.

• Extremes of heat and cold, sun and shade, wind or the lack of it, and glare can adversely affect use.

• The suburban building setback requirements rob us of the enclosure and scale that make us feel comfortable. And to compound matters, there is nothing separating us from the automobiles except 2 or 3 feet of grass.

• The typical suburban street design sequence goes something like this: four-lane divided arterial, sidewalk, 10 feet (if you’re lucky), landscape strip, parking lot, building.

• The kind of design sequence that most pedestrians prefer goes like this: street, on-street parking, tree-planting verge, sidewalk, building,parking lot.

•William H. Whyte observed in his study of small urban places, people want to go where other people are.2 They are drawn to popular shopping, recreation, and entertainment centers to interact with and observe others.

• Jane Jacobs offered some insight into this phenomenon in her book, The Life and Death of Great American Cities.

• She suggested that there is a correlation between the amount and variety of activity associated with a sidewalk and whether people use it.

• She introduced the concept of networking of activities, which is the integration of both the amount of diversity included along the walk and the variety of interest it offers to potential users. An intricate mutual support or functional mixture must develop before there is an incentive for pedestrians to use it. And, she stressed, the more diverse the activity and opportunity, the more pedestrians are likely to use it.

• The ultimate goal is to meet the user’s need for enclosure while providing a safe, comfortable, and interesting place to interact with others.

• Pedestrian ways should be integral circulation routes to specific destinations in the community. They must go where people need and want to go.

• Plan for novelty. Create alternate routes to the same destination. Allow for individual variation. People get bored if there is only one way to go.

• The concept of networking can be used to create a cohesive balance of function and amenity along the way. A hierarchy of social gathering spaces adjacent to or bisecting the pedestrian artery will enhance its usefulness to the user.

• A choice of activities, both active and passive, provides something for everyone.

• Every location is unique. Avail yourself of every opportunity to enhance the walking experience. If we want people to get out of their cars, it has to be convenient, worthwhile, and perceived as a gain rather than a sacrifice.