Study Guide Ch. 7 Buildings and Circulation Flashcards
Site Design LARE
Design choices should always be oriented around promoting health, safety, and welfare of site users
As well as minimizing development impacts to the site
Establishing the location and orientation of a proposed structure is often the first opportunity that a designer will have to determine a project’s character, as well as the extent of disturbance to a site
Note that commercial uses are especially sensitive to building location given that proximity to customers, ease of access and visibility all directly impact the success of a business
Buildings should be located according to the following principles:
- locate buildings on previously disturbed sites if possible. Doing so conserves open space, minimizes construction disturbance and reduces costs, among other things
- locate structures with respect to site topography to minimize grading
- locate structures as close to existing access points as possible to minimize road length. Longer roads increase development costs, result in more impermeable surface and increase overall development impacts while also reducing pedestrian safety.
- locate buildings such that their impact on existing vegetation is limited
- buildings - and especially building entrances - should have a southern orientation, with SSE and SSW being the most ideal, as this promotes solar gain during winter months.
- building entrances should be placed along major pedestrian pathways
Scale, massing and character
2-4 stories is human-scale
A building’s scale is determined by its massing and articulation, and buildings should be well-articulated for at least the first two stories to feel in scale with human users.
Human-scaled streetscapes are therefore enclosed by buildings that are two to four stories in height, with any height stories being recessed, or “stepped back”
Scale, massing and character
Articulation is good
Long, unbroken expanses of building facades feel imposing and monotonous to pedestrians, and articulation (e.g., large, transparent windows) should be introduced to convey a human scale and create a more inviting streetscape
Scale, massing and character
Consider wind and shade
Taller buildings (generally in excess of 10-12 stories) should be designed such that they do not cast shadows or create a wind tunnel effect toward streetscapes and public spaces.
Breaking the building mass up into smaller units can often mitigate the negative impacts caused by tall buildings.
Scale, massing and character
Reduce energy use
The energy demands of a building can be lowered by reducing its surface area, building it to a human scale and by increasing the provision of natural light and ventilation inside the structure
Scale, massing and character
Footprint = impact
The development impacts of a building can be lowered by reducing the size of its footprint
Site circulation
Vehicular, pedestrian, bicycle and multi-user
Placement and extent of site circulation can have a significant impact on the extent of disturbance caused by construction activities. As such, it is critical that any circulation systems be designed to minimize their impact on critical site resources, while also ensuring the health, safety, and welfare of site users.
Considerations when designing site circulation
- connectivity
- align entries and exits
- visible entries and exits
- establish a hierarchy
- facilitate wayfinding
Connectivity
New site circulation elements absolutely must connect to existing circulation systems serving the site
Align entries and exits
Site entry and exit points must be located along the site periphery, and they must be aligned or otherwise coordinated with entry/exit points and intersections found in the surrounding areas
Visible entries and exits
Site entry and exit points should be clearly visible and - if multiple entry/exits exist - the designer should establish a hierarchy among these entry/exit points
Establish a hierarchy
Site circulation should always have a clear hierarchy.
Whether through scale (e.g., larger streets) or visual character (e.g., high-end material finishes and high level of detailing vs. none), the relative importance of circulation paths should be clear to site users.
Note, however, that all major circulation paths should lead to site entry/exits and key site features
Facilitate wayfinding
Wayfinding aids such as signage are one means to help users orient themselves on a site.
Clear sight lines, vantage points/overlooks and site landmarks (e.g., monuments, iconic buildings) also help facilitate wayfinding across a site.
Wayfinding can also be facilitated through breaking the site up into “regions” that use a visual language (including plantings and hardscape selection) to differentiate themselves.
Note that color is often a poor choice for wayfinding signage, given that color does not convey hierarchy and that most people have difficulty distinguishing between shades of the same color. Also note that color-coded signage does not accommodate the needs to sight-impaired and colorblind site users.
Exceptions
Hospitals do not follow all of the site circulation principles outlined. Hospital campuses should be divided into public and private/secured zones for the safety of both site users and patients, and patient recreational areas and patient intake should be located inside the private zone. Also note that private, on-campus circulation should be self-contained and not connect to adjacent public roadways.
Roadways are organized by the functional classification system, which defines the relative traffic-carrying capacity of a street.
There are four general classifications for roadways, and they are as follows:
Principal Arterial
Minor Arterial
Collector
Local
Principal Arterial
Also referred to as major arterials, highways, or controlled-access highways, this class of roadway is designed to carry large amounts of traffic long distances between major urban areas at high speeds.
Note that major arterials typically have controlled access, that is, they can only be accessed by specific connecting roads (typically, highway on-ramps)
Minor Arterial
These roadways provide continuous routes through urban areas and most major commercial and institutional uses will be located along minor arterial roadways.
Planning and Urban Design Standards refers to minor arterials as the “backbone” of the urban street network.
Note that residential sites do not typically have direct access to a minor arterial-class roadway.
Collector
Collector roads are used to link traffic from local streets to minor arterial roadways.
Note that some residential sites have access to collector roads.
Local
The lowest class of roadway, local roads include any street that does not fall into the categories described.
Local roads are typically short (used only to connect to the nearest collector road) and include numerous traffic control devices (e.g., stop signs) to maintain low speed limits.
Note that most residential sites have access to local roads, and that local roads comprise 90% of all streets in the United States, while carrying only 10% of the total traffic volume.
Roadway Patterns
Four basic categories
Grid pattern
Radial pattern
“Classic” pattern
Linear system
Planning and Urban Design Standards
Classifications of Roadway Patterns
Grid
Grid and Squares
Web
Radial
Curvilinear
Irregular
Grid Pattern
Advantages
- Easy to navigate due to simplicity and regularity of their design, as well as their high degree of connectivity
- Provide users with straightforward access to properties, and function best in flat land and in situations where a complex, distributed flow of traffic is preferred
- High levels of connectivity also tend to reduce traffic congestion by distributing traffic across a greater number of streets, rather than concentrating traffic on a small number of arterial or collector streets
- Note that they are also popular with property developers because they provide the most lots per linear foot of street among all roadway patterns
Grid Pattern
Disadvantages
- Tend to be visually monotonous, and their straight roads will often encourage higher vehicle speeds
- Moreover, they have no clear hierarchy and - due to their regular pattern - grids are poorly suited to areas with complex topography and critical natural features
Radial Pattern
Advantages
Emphasize clear and direct lines to and from a central point
Radial Pattern
Disadvantages
Travel that occurs outside the radial lines is typically inconvenient, and radial patterns
- tend to create oddly shaped property boundaries and building sites
“Classic” Pattern
Advantages
- Establishes a clear hierarchy of streets that can service multiple points of interest
Due to its flexibility, this pattern works well in areas with topography and important natural features
“Classic” Pattern
Disadvantages
Tends to perform poorly in situations where traffic or other interruptions occur along an important arterial roadway.
The classic pattern therefore has multiple critical points of failure due to its relatively low levels of connectivity.
Linear System
Advantages
Typically constructed in response to a pre-existing linear element (e.g., railroad, shoreline, canal, highway), linear systems provide convenient flow along one axis
Linear Systems
Disadvantages
Do not tend to accommodate travel among other axises, and they have a relatively poor hierarchy
Horizontal roadway alignments are composed of two basic geometric components
Straight lines
Arcs
Horizontal road alignments
- Road alignment should be as direct as possible, while also addressing topography and other critical natural or cultural features on a site
- all straight lines should be tangent to any arcs (curves) in the roadway (as measured from the roadway’s centerline)
- longer curves in the roadway tend to be safer than tighter curves
- abrupt changes in road character should be avoided if possible (e.g., straight roadway that transitions to a sharp curve or s-curve)
Component of a curve
PC: point of curvature (beginning of curve)
PI: point of intersection (point at which the tangents intersect)
PT: point of tangency (the end of the curve)
C: chord (distance between PC and PT)
Vertical road alignments
Intersections and site entry/exits should not be placed in locations with steep topography due to sight distance criteria, as well as the danger that steep slopes pose during inclement weather
Sight Distance
Length of road ahead of the vehicle that is visible to the driver.
Note that both horizontal (curves) and vertical (hills) changes to the roadway impact sight distance.
What are determined by site distance requirements
Roadway alignments
Speed limits
The location of intersections
Site entry/exit points
Minimum site distance that exists along any portion of the roadway should allow …
A vehicle (traveling at or below the speed limit) to stop before reaching an object in its path
Note that sight distance has a direct impact on general road safety, including protecting pedestrians and cyclists that are sharing or crossing the roadway.
In situations where the sight distance is insufficient, what can be used to improve sight distance conditions prior to attempting to re-align the roadway itself
Pruning vegetation
Relocating obstructive elements (e.g., signage)
Eliminating street parking (if it is blocking a driver’s line of sight)
Sight Triangle
A site distance located at an intersection
When located at an intersection, the drive must have sufficient sight distance to the intersecting roadways, thereby creating the sight triangle
Sight triangle is determined by
Line of sight
Design speed of roadway
Note that the sight triangle must be free from any obstructions, including trees and other vegetation. As a general rule, any plants located in the sight triangle should be no higher than 2 ft.
Three basic ways in which roads can relate to topography
Parallel to the slope
Perpendicular to the slope
Diagonal across the slope
Parallel to the slope
Advantages
Results in easy access between road and buildings
Parallel to the slope
Disadvantage
Building orientation disrupts the natural drainage pattern, therefore the proposed grading must direct the stormwater runoff around the buildings
Perpendicular to the slope
Advantage
Building orientation is more conducive to the natural drainage pattern
Perpendicular to the slope
Disadvantages
Roads will likely be steep given that the steepest slope occurs perpendicular to the contours
Awkward relationship between road and buildings (paths or drives places perpendicular to the direction of the road just be cross-sloped)
Costly grade changes may be required between buildings (e.g., retaining walls)
Diagonal across the slope
Advantages
- Efficient storm drainage design
- Good access between the road and adjacent structures
- Gradients less steep than in a perpendicular orientation
- Results in the least amount of disturbance to the landscape
Parking lot design issues in section 3 focus on location of lot and any safety issues that might occur from placement of parking and passenger drop-off areas
Note that parking is generally framed as an issue for sites without single-family residential uses
When siting a parking areas and passenger drop-off, the following best practices apply:
Minimize disturbance
Make parking convenient
Flat sites
No dead ends
Separate pedestrians and vehicles
Create safe drop-offs
Minimize disturbance
Site parking area in location that will not disturb existing site resources, and - if asked to consider drainage patterns - ensure that the parking lot does not drain in wetlands or natural hydrological features
Make parking convenient
Locate parking areas near building entrances if possible, and note that most site users will be unwilling to walk more than 700 ft. (1/8 mile) from their parking space to the building entrance
Also note that ADA parking spaces should be nearest to the building entrance.
Flat sites
Parking areas should generally be located on a slope of between 1-5%
No dead ends
Parking lots should not contain dead ends.
If a dead end is part of the existing conditions, a hammerhead-style turnaround can be added to assist in traffic flows
Separate pedestrians and vehicles
Site the parking area such that it minimizes interaction between the main site and traffic/circulation network and pedestrian users
Create safe drop-offs
Site drop-offs outside the main traffic flow and located the drop-off area on the passenger’s side of the vehicle
Note that business owners often prefer that parking areas are located in highly visible areas for ease of customer access.
Deign best practices generally state that parking areas should be located behind buildings to provide a more engaging and active streetscape.
Most non-residential uses will require access for shipping and receiving activities, and these should be located away from the public parking area.
Reducing parking lot size
Options to reduce impervious surface
- pervious material preserves total prkg quantities w/o altering any dimensions
- dimensions of the parking stalls could be reduced preserving total prkg quantities and allowing for portion of lot to be demolished
- dimensions of parking aisles could be reduced
- total parking quantities could be reduced by integrating mass transit into the site
When adjusting dimensions of parking areas, the smaller the angle that parking stalls are configured …
The narrower the cross-section of a parking lot will be
45-degree angle stalls would require a narrower drive aisle than a 60- or 90-degree, with the 90-degree stall requiring the largest cross-section.
When accounting for total parking numbers, the 90-degree angle stalls accommodate the most cars per sq. ft. and 45-degree stalls the least
Traffic calming highly likely to be on section 3 exam
Traffic calming techniques
Speed bump
Raise crosswalk
Speed table
Raised intersection
Neckdowns
Traffic circle
Roundabout
Choker
Realigned intersection
Textured surface
Center island narrowing
Chicane
Woonerf
Raised crosswalk
Speed bumps with flat tops marked for pedestrians crossings
Bring the street up to the sidewalk level, increasing pedestrian visibility and safety
Speed table
Flat-topped, raised platform that is long enough for both wheels of a car to be on top of the table at the same time
Raised intersection
A flat-topped areas that covers the entire intersection
Usually raised to sidewalk level, approximately 6 inches
Neckdowns
Curb extensions at intersections used to reduce the roadway and crosswalk width
Also called bulbouts, curb extensions, or intersection narrowings
Traffic circle
Raised island located at an intersection around which traffic circulates
Are used on residential streets in lieu of four-way stop signs
Roundabouts
Circular raised islands installed at intersections on higher-volume streets such as collectors and arterials are are often used in place of traffic signals or four-way stops. They require yield-at-entry design.
Choker
Narrowing devices similar to neckdowns
They are used at mid block to narrow the street and slow drivers
Realigned intersection
Used at t-intersections, these realign a straight approach into a curve to slow vehicles
Textured surface
Usually used in conjunction with other traffic calming devices, but may be used alone
Center island narrowing
Raised islands located at the centerline of a street to narrow road width and slow drivers
Chicane
Streets in which curb extensions alternate from one side of the street to the other, thereby creating S-shaped curves.
They reduce both speed and volume, and their design must prevent cut-through driving down the centerline
Woonerf
A type of roadway design originally implemented in the Netherlands, in which traffic-calming measures, low speed limits, and shared space between various roadway users are provided to increase safety within the right-of-way
Streetscape
The various built elements that comprise a street, including the road, adjacent buildings, street trees, open spaces, sidewalks and site furnishings
Discussions related to streetscapes typically involve aesthetic considerations, but streetscape design can impact broader patterns in urban environments
The number and distance of vehicle trips can be reduced not only by mixing land uses and providing mass transit options, but also by creating shorter blocks (between 300-500 ft.) and providing amenities (e.g., site furnishings) that improve neighborhood walkability
Five categories that comprise a streetscape
Paving
Planting
Lighting
Furnishings
Public and Private Amenities and Facilities
Paving
Considered to be the most visually prominent component of a streetscape, paving materials should be selected based upon local climate conditions and other safety considerations, as well as the overall character of the streetscape in question.
Note that colored paving or changes in materials and texture can be used to design street hierarchy, add visual interest and increase pedestrian safety (e.g., emphasizing the presence of a crosswalk to drivers).
Overly complex paving patterns may disorient users with visual impairments and should be avoided in public areas
Planting
Street trees and other plant material provide shade and improve general air quality, while also contributing to the visual character of a street.
They can also provide a physical barrier and visual barrier between the roadway and the sidewalk, thereby increasing pedestrian safety.
Note that street trees should be placed uniformly and should not be located within the sight triangle at intersections.
Distance of tree spacing can be determined by site conditions, but trees should not be spaced closer than their canopy diameter at maturity.
Note also that streetscape plantings require consistent maintenance to avoid safety issues such as low branches that block views to and from the roadway, fallen leaves that clog stormwater inlets, and roots that crack pavement.
Lighting
Used to enhance visibility for vehicles, cyclists, and pedestrians, thereby creating a safer streetscape.
Should generally be located between the sidewalk and the roadway, and it can often be located inside planting beds to facilitate pedestrian pavement on hardscape surfaces.
Can also facilitate wayfinding, especially when key buildings, signage, or pathways are emphasized in the lighting design.
Note that lighting - especially streetlights - should also be spaced at uniform intervals, with the one exception being accent lighting used to highlight key site features.
Lighting (part 2)
While it may seem intuitive to light the streetscape as brightly as possible to enhance public safety, such a strategy is not necessary, nor may it be particularly desirable to residents whose homes front a brightly lit streetscape.
Outdoor lighting does not need to use high levels of illumination if a clear and consistent lighting scheme is developed.
Light pollution and energy use are always a consideration when designing outdoor lighting, so one would also want to avoid using upward-facing light fixtures (which increase light pollution).
Furnishings
Not only provide character to a streetscape, they also perform numerous critical functions.
Benches provide a resting area for pedestrians
Bike racks allow cyclists to store their bicycles in a secure and orderly fashion
Bollards prevent vehicles from entering pedestrian areas
Trash receptacles reduce the frequency of litter.
Note that street furnishings should be located on either side of a sidewalk (i.e., street-side or building-side)
If located toward the street side - and not servicing mass transit or another use located along the roadway - furnishings should be separated from the roadway by a planting area if possible.
Site furnishings should generally never be located in the middle of circulation path, as this would pose a safety hazard to site users.
Note that when selecting seating “L” shaped benches are generally recognized as the seating shape most conducive to encouraging interaction between site users (given that the “L” shape orients users toward one another)
Public and Private Amenities and Facilities
Includes public utility boxes and parking meters, as well as various elements (e.g., signage, outdoor dining areas) introduced by private business owners along the streetscape.
As with site furnishings, these elements should be oriented toward either side of a sidewalk and not impede the flow of pedestrians in the streetscape.
Building scale
Plays an important role in defining the streetscape due to the sense of enclosure that buildings can provide.
Architecture directly impacts streetscape character. Locating driveways, garages, parking lots, and drive-throughs away from pedestrian areas enhances pedestrian safety and leads to more aesthetically pleasing streetscapes.
And building entrances, windows and other articulation oriented toward the streetscape increase visual interest and improve safety and surveillance.
Complete streets
Streets designed and operated to enable safe use and support mobility for all users, regardless of their mode of transportation.
Look to provide safe pedestrian and cyclist infrastructure, encourage the use of mass transit, and they often make use of traffic-calming measures to lower automobile speeds.
Pedestrian circulation systems at a site scale should always
- Provide access to and from the site
- Mobility within the site
- Access to any public or recreational spaces on the site
Site entries and exits should be
- Highly visible
- Connect to existing circulation networks outside the site
Maximum distance most pedestrians are willing to walk to reach their destination
700 ft (1/8 mile)
Most relevant to travel within a discrete site or activity (e.g., walking from a parking space to a restaurant)
Depending upon scale of site, rest areas may be required to make the site accessible to certain site users
Pedestrian shed
1/4-1/2 mile
Can be applied to situations that are not as well-delineated (e.g., walking in a city center while shopping at several stores)
Note that sidewalks within the public right of way - generally considered to be the backbone of pedestrian circulation systems - are often required by a municipality to be maintained by the adjacent property owners, with many public agencies stipulating that a professional contractor must be hired to conduct any work or maintenance
Design criteria that should be applied to the development of a pedestrian circulation system
Separation
Connectivity
Capacity
Accessibility
Amenities
Separation
Pedestrian circulation systems should be designed to minimize pedestrian conflicts with vehicles and cyclists, and this is best accomplished by separating pedestrian areas from those used by other forms of transportation.
Pedestrian systems should also provide substantial access to pedestrian-only areas.
When pedestrians and vehicles and/or cyclists intersect, pedestrian areas (e.g., crosswalks) should be clearly identified through signage, pavement changes and other markings
Connectivity
In addition to connecting with existing circulation systems both inside and outside the site, pedestrian circulation should follow “desire lines” to important features or locations.
Note that connectivity should not come at the cost of clarity; that is, the designer should minimize interruptions to the pathway system whenever possible.
Capacity
Pathway widths should correspond to a hierarchy (i.e., wider paths are more important) and be scaled to accommodate anticipated pedestrian traffic
Accessibility
The pedestrian circulation system should service the needs of all users, and disabled users should be given direct access from parking areas to walkways and building entrances.
Accessibility also implies that pedestrian surfaces and pathway gradients are safe to use in all weather conditions, and that rest areas are provided as needed.
Amenities
Enhance the usability of the pedestrian circulation system, and they include site furnishings, signage, vegetation, site lighting and special material treatments (e.g., paving) to define points of interest
Pedestrians are exposed to the greatest danger when they interact with
Other modes of transportation, particularly automobiles
This occurs most frequently at street crossings
Pedestrian safety at intersections can be increased by:
- ensuring that vehicles and roadway users have unobstructed visibility to all crosswalks. Note that unobstructed visibility should be the primary criteria when designing a crosswalk.
- orienting all crosswalks perpendicular to the roadway
- reducing the distance required to cross a street, typically through pedestrian islands or curb extensions known as “bulb-outs” or “Neckdowns”. Note that mid-block crossing locations should make use of “bulb-outs” or pedestrian islands whenever possible, as drivers are less vigilant of pedestrians crossing a roadway when not at an intersection
- lower vehicle speeds
- if designing a new roadway, narrower roads typically enhance pedestrian safety
- visible signage and flashing lights
Note that the CLARB-approved texts generally discourage the use of grade-separated crossings (e.g., pedestrian overpasses or underpasses) because they are often steep and difficult to negotiate for people with physical impairments. In addition, grade-separated crossings are typically expensive to construct.
Types of bikeways
Most safe to least safe
1. Bicycle paths
2. Bicycle lanes
3. Wide outside lanes
4. Shared roadways
Bicycle paths
Dedicated lanes for bicycle traffic separated from vehicles either by open space or barriers within an existing roadway, or exist as a right-of-way independent from vehicle traffic.
Bike paths are:
- generally 8-12 ft. wide
- a maximum 2% cross-slope, with 1.5% considered ideal
- typically paved with asphalt. Asphalt allows for greater accessibility and is more durable than gravel and concrete is typically more expensive, and concrete joints create disruption in the bike path surface
Bicycle lanes
A portion of a larger roadway that is designated for use by bicycles.
Bicycle lanes are delineated by signs, markings, or textured strips within the right-of-way, and they are generally 5-6 ft. wide.
Note that bicycle lanes can be integrated into an existing right of way by:
- narrowing existing vehicular travel lanes
- removing a vehicular travel lane
- removing street parking
- widening the roadway
Wide outside lanes
Located on the right side of traffic and are intended to be shared with vehicles in the roadway without impacting traffic flow.
Wide outside lanes are typically ~14 ft. in width because they are designed to accommodate bicycle and vehicle traffic simultaneously
Shared roadways
Are the most dangerous form of bikeway
Signage may be used to indicate the presence of a shared roadway, but bicycles are, in essence, treated as automobiles.
This has the potential to impede traffic flow, as any vehicle wishing to pass a bicycle must do so by moving into the left-hand lane.
As a general rule, wide outside lane and shared roadway configurations should only be used on low-speed, low-traffic streets.
Streets with higher traffic volumes and speeds should provide dedicated bicycle lanes or bike paths to safely accommodate cyclists.
Note that all bikeways are typically designed to accommodate users traveling up to 20 mph, and all should provide an overhead clearance of at least 10 ft.
Regardless of bikeway configuration - whenever bicycles share the roadway with vehicles, they are at risk, and accidents occur most frequently when
- cyclists turn left across oncoming traffic
- cyclists cross an intersection when vehicular traffic is entering from or turning from the right
- either/both bicyclists and motorists fail to yield
Criteria to take into account when designing bicycle circulation networks:
- adequate sight lines that provide safety for all users
- topography that is conducive to use by cyclists (8-10% slopes are acceptable over moderate distances, and grades of excess of 10% should be avoided if possible)
- adequate lane widths to accommodate cyclists
- safe conditions at all intersections and other dangerous conditions
- appropriate signage, markings and striping are provided
- adequate drainage infrastructure to prevent water from collecting in the right-of-way
- pavements that meet climate, maintenance and design considerations
- integration with existing bicycle networks
Note that bicycle circulation networks tend to be most successful when they are
- safe
- provide direct connections to destinations
- have minimal topography
- allow cyclists to travel uninterrupted, or with a minimum of interruptions (e.g., stop signs at intersections)
Rails to trails
Note a that abandoned rail tracks are sometimes re-designed as bike paths (or multi-user trails)
This form of creative reuse takes advantage of the adequate width and gentle slopes that characterize most rail infrastructure and has become an increasingly popular means of providing outdoor recreational opportunities to the public.
Multi-user trails designed to
- accommodate a range of users, including walkers/hikers, bicyclists, and inline skaters
- provide opportunities to a broad range of physical fitness levels, and this sometimes means providing alternate routes with more or less challenging features (known as a “graduated difficulty of access”)
- trails within each trail system should be marked with signage that indicates relative difficulty, recognizing that not all trails will be accessible to all users
- users should be given the opportunity to select a trail that matches their goals
Note that the bulk of the multi-used trail system should be designed to be accessible by the broadest cross-section of users as possible
- main trail networks should be paved and designed along gradients of leas than 5% so that they meet ADA requirements
CLARB: primarily used for recreation, with fitness, transportation, and commuting being secondary concerns for the majority of trail users
Multi-user trails should be designed such that they:
- are located within open space or linear park areas away from traffic and the built environment
- provide a sense of connection of local ecosystems
- bring users to a variety of destinations
- are connected to a broader circulation network
- minimize interruptions and impediments to travel
- avoid steep slopes
- feel safe for all Trail users and undergo routine maintenance
- provide amenities (e.g., benches, rest areas, interpretive signage) that encourages extended and repeated use
Lighting
Note that many multi-user trails will include lighting, even if this lighting is limited to trail entry/exit points and intersections
“Nature trails”
Generally designed to different criteria than multi-user trails
Usually surfaces with natural soils or crushed aggregate
Designed to follow the surrounding topography
Grades on nature trails will vary: easy trails 3-5% slopes on average, moderate trails 8-10%, strenuous trails averaging slopes in excess of 10%
Conflict on multi-user trails
Although an important public resource, conflicts between various users is a significant concern.
Most accidents occur between cyclists and pedestrians and are caused by unsafe behavior or overcrowding
To increase safety for all users,
Trails should be of sufficient width
And/or dividing the trail into well-delineated lanes or “treads” (i.e., surface area) for each type of user
Trails without sufficient width may also separate users under a time-of-use policy that restricts specific uses to certain days or hours
Signage
All trails should contain signage that outlines appropriate conduct for each type of user (e.g., cyclists, pedestrians)
Note that involving each potential trail user group in the design process is the best way to both understand local needs and resolve the potential for conflict on multi-user trails
Universal and barrier-free design principles advocate for site design and site features that allow access to the broadest possible range of people
More accessible a site to a wider range of users, more they are able to benefit from ecological, social, or economic opportunities that it provides
Basics
- ADA-accessible parking spaces should be located as close as possible to building entrances, as well as to the shortest accessible path of travel to buildings in general
- all ADA-accessible routes must be continuous and free from obstructions
- all ADA-accessible routes must follow the route planned for the general public to the greatest extent possible
- the primary elements and spaces of a site (i.e., parking, entrances, buildings) must be ADA accessible
Key ADA Measurements
- according to the ADA, whenever a walkway exceeds 5% (one foot of elevation change over 20 horizontal feet), is is considered a ramp
- the maximum slope for any ADA-accessible walkway (including ramps) is 8.33% (one foot of elevation change over 12 horizontal feet)
- ADA-accessible walkways without handrails should have a maximum cross slope of 2.1% (1:48) and ramps should have a maximum cross slope of 2% (1:50)
Specific Design Considerations
- stairways are the most significant barrier and hazard to site users with disabilities
- any level change (e.g., curbs, stairs) presents a potential safety hazard to a disabled site user
- although ramps are necessary for those in wheelchairs, they are not necessarily easier for other users with physical disabilities. As such, ramps and stairs should be provided together whenever possible.
- handrails are critical to an accessible landscape. Without them, steps, ramps and other grade changes are very difficult to navigate for site users with physical disabilities
- paving materials strongly influence accessibility, especially in regions with rain, snow and ice
- tactile warning strips should be used to delineate edges and along any site furnishings that cannot easily be detected by a guide cane
- bollards should never be placed in the center or main flow of a pedestrian walkway
- chain barriers are especially dangerous to site users and should not be used. To be detected by a guide cane, they need to be located low to the ground, but when located low to the ground they become a trip hazard for all other site users
Note that site amenities such as seating, restrooms, shade structures and water fountains make a site easier to negotiate for both disabled and non-disable site users.
Accessible design is best approached as an opportunity to meet the needs of all site users.
Elderly Site Users
- elderly site users are generally characterized by diminished perceptual abilities, specifically as this relates to sight and hearing
- elderly site users have particular difficulty seeing small changes in grade. Visual cues should be provided at all grade changes to reduce the risk of tripping and falling accidents among elderly site users.
- comfortable seating will lead to more active and better functioning spaces for elderly site users
- walking is the most common exercise activity for elderly Americans and walking paths can help foster social interaction between the elderly and other populations
- playgrounds and daycare facilities are considered to be complimentary uses for elderly site users because the sight and sound of young people playing is (often) greatly appreciated by the elderly
