Critical Review of the Cary Design Guidelines Manual with Regards to Bicycle Transportation

Steven Goodridge, Member, Cary Planning and Zoning Board

 The Cary Design Guidelines Manual, published online by the city of Cary, NC at http://www.townofcary.org/depts/dsdept/P&Z/Carydesi.pdf , is intended as a guide to assist developers with designing new communities within Cary in ways that provide functional benefits that Cary residents appreciate. The manual identifies a number of founding principles, including creation of human scale, creation of sense of place, connection of uses, and planning for pedestrians and bicyclists. The manual then provides specific recommendations for design elements intended to implement those principles. The purpose of this paper is to critique the design elements that the Guidelines Manual recommends for bicycle transportation.

Connection of Uses

The first principle of the Cary Design Guidelines Manual that relates directly to cycling transportation is Connection of Uses. Many suburban developments in North Carolina feature poorly connected, hierarchical road topologies that direct nearly all useful trips onto arterials and make it difficult or unpleasant to cycle from one type of land use or development to another. The Cary Design Guidelines Manual recommends that neighborhoods and activity centers be well-connected with multiple, redundant routes, including convenient ways to reach adjacent land uses without requiring use of an arterial. This principle serves transportation cyclists well by shortening trips to nearby shopping centers and schools, and by providing low-traffic alternatives to arterials for those cyclists who find low-traffic routes to be more pleasant or less challenging.

Figure 1: Illustration from the Cary Design Guidelines Manual showing street connectivity that disperses traffic, shortens local trips and allows a choice of routes.

Figure 2: Illustration from the Cary Design Guidelines Manual showing how roads within developments make them permeable to cyclists and provide alternatives to arterials for short trips.

Planning for Bicyclists

Although most cycling transportation is done on ordinary roadways, the Cary Design Guidelines Manual includes facility design recommendations specific to bicycling. Some bicycle-specific facilities can enhance the efficiency, enjoyment or safety of cycling, but many facility designs have significant disadvantages. The Cary Design Guidelines promotes both good and bad implementations of cycling-specific facilities, as shown below.

The Cary Design Guidelines Manual defines "bicycle routes" as follows: 

"Bicycle routes include: designated bike paths;  shared pedestrian-and-bike facilities such as greenways, paths, and sidewalks; and on-street bike lanes. 

The Manual omits mention of ordinary roads. Most ordinary, well-designed and maintained roads make excellent bicycle facilities; most of the miles traveled by bicycle are on conventional roads. On busy roads, often all that is needed to make roadway cycling more comfortable is a slightly wider outside through lane to allow more passing space. Omission of any mention of ordinary and wide outside lanes from the bicycling section of the Manual is unfortunate, because the Manual may consequently encourage unnecessary and undesirable segregation-oriented engineering that often serves cyclists less well than conventional shared roadways, while also costing more to construct and maintain. For a discussion of some of the problems that can be caused by the addition of vehicle-type segregation stripes to otherwise good wide-laned roads, follow this link.

The manual continues: 

"It is a goal to conveniently and safely provide bicycle connections between most destinations."

All destinations in Cary are served directly by ordinary streets where roadway bicycle travel is allowed under state law. All such roadways should, therefore, be designed, maintained, and patrolled by law enforcement to be reasonably safe for cycling. This makes safe bicycling connections available to all destinations, not most. However, it is certainly not always possible to make all destinations convenient to reach, even by car.

Off-Road Greenways

The Cary Design Guidelines Manual concentrates its cycling discussion on off-road pathways that bicyclists would share with pedestrians. Off-road paths that follow their own right-of way (also known as greenways) can sometimes be very pleasant places for casual or family cycling, and sometimes provide useful connections to destinations. In order for these paths to perform as safely as expected for the novice cyclists they are intended to serve, it is important that they cross streets with full grade separation, as shown in Figure 3. The Cary Design Guidelines Manual recommends grade separation where possible. An example of an existing fully-separated off-road Greenway in Cary is the Black Creek Greenway extending from West Dynasty Drive to Crabtree County Park.

Figure 3: Illustration from the Cary Design Guidelines Manual showing a grade-separated path crossing. (a) is the roadway; (b) is the greenway.

Sidewalk Bike Paths

Problems arise when bike path designers attempt to serve denser, more urban destinations via off-road paths. Most urbanized areas have frequent streets; this usually makes grade-separated crossings cost-prohibitive or topographically impossible. Right-of-way space for completely off-road paths may not be available either. As a result, facility designers are often tempted into running bike paths alongside roads as sidewalks, crossing roadways at crosswalks. Most respected engineering publications on safe cycling facilities strongly recommend against such parallel paths in areas there there are driveways or intersections. Sidepaths such as these are generally more dangerous than cycling in the roadway because of the unexpected hazards that sidepaths pose at junctions such as intersections and driveways. Cycling crashes and injuries are between two and ten times more common per cycling mile on sidepaths compared to cycling on the adjacent roadways. Unfortunately, the Cary Design Guidelines Manual encourages bicycle-sidepath design, as shown in Figures 4 and 5. 

Figure 4: Illustration from the Cary Design Guidelines Manual showing sidewalk-style bike paths running alongside roads and crossing at crosswalks.

Figure 5: Illustration from the Cary Design Guidelines Manual showing a sidewalk-style bike path running alongside a road. Although the landscaped buffer is attractive and provides the illusion of safety, the vast majority of car-bike collisions occur at driveways and intersections, which are still necessary to connect the developments on the left of the path with the roadway on the right. Riding on parallel paths such as sidewalks is several times more dangerous than operating on the roadway section; sidewalk cycling is the leading cause/contributor to car-bike collisions in Cary.

In The Traffic Safety Toolbox published by the ITE (1993, page 208) we read:

"Sidewalk bike paths. From the late 1970s through the mid-1980s a number of communities signed some sidewalks or built new paths for bicyclists parallel to roadways. Several states even passed laws forcing bicyclists to use such facilities if they existed. Bicycle/car crashes increased dramatically in some corridors, especially at driveways, intersections, on bridges, and other locations. Sidewalk paths parallel to a roadway force bicyclists to ride against traffic half of the time. In either direction, motorists are often surprised by the presence of cyclists [on sidepaths], since [motorists] are neither conditioned nor capable of searching these locations for traffic moving at 8-15 mph. Many pedestrians were also hurt, or complained that it was no longer comfortable to walk. Also, many motorists became less considerate of bicyclists who continued to use the often safer roadway sections.…in no case should a bicyclist be forced to use the sidewalk pathway. Never sign a sidewalk or parallel path as a bikeway, since many motorists who see these signs will assume that those bicyclists riding on the roadway section are not permitted to be there."

The 1999 AASHTO Guidelines for the Development of Bicycle Facilities specifically warns against sidewalk bicycle riding: "...Sidewalks are typically designed for pedestrian speeds and maneuverability and are not safe for higher speed bicycle use. ... At intersections, motorists are often not looking for bicyclists (who are traveling at higher speeds than pedestrians) entering the crosswalk area, particularly when motorists are making a turn. Sight distance is often impaired..."

For more about why sidepaths (sidewalk-bike-paths)  are a bad idea, see John Allen's related articles here.

Door-Zone Bike Lanes

Another inappropriate and potentially dangerous bicycle-specific design treatment advocated in the Cary Design Guidelines Manual is a door-zone bike lane. Cycling safety instruction (including the advice printed on Cary's own bike map) teaches cyclists to keep their right side more than four feet away from the side of a parked car in order to avoid the possibility of colliding with a suddenly-opened door. Such dooring incidents are a frequent cause of crashes to cyclists in urbanized areas. Instead of encouraging cyclists to stay far enough to the left, out of the door zone, door-zone bike lanes lure many unsuspecting cyclists into this hazardous area. This can lead to tragedy.

Figure 6: A door-zone bike lane that encourages or mandates cyclists to operate too close to parked vehicles, where cyclists will not be able to stop in time to avoid suddenly-opening doors. Cycling safety classes and materials teach cyclists to stay out of this area. Learn more about the dangers of door-zone bike lanes here. (Also, more here.)

Bicycle Parking Issues 

The Cary Design Guidelines Manual encourages developers to provide bicycle parking. From the Manual: 

"Provide facilities to store or lock bicycles at appropriate sites, including schools, major recreation areas, transit stations, office parks, public institutions, and activity center focus areas." 

Bicycle parking is important for transportation bicycling, because a lack of secure and convenient parking facilities can deter cycling or lead to bicycle damage or theft. The Manual provides pictures of a variety of bicycle parking facilities without describing the advantages or disadvantages of the designs. One of the example photos provided is the ubiquitous, but undesirable, "comb-rack" as shown in Figure 7. The Association of Bicycle and Pedestrian Professionals recommends against comb-racks because they do not afford use of secure U-locks without parking the bicycle sideways and taking up the entire rack. A more desirable rack that accepts U-locks, chains, and cables is a simple and compact inverted-U.

Figure 7: From the Cary Design Guidelines Manual: A vertical "comb" bike rack that is designed to hold a bicycle by only the front wheel. Such an intended position does not allow the use of normal U-locks to secure the bicycle frame, and makes the bicycle vulnerable to a bent front wheel. It also requires an excessive amount of mostly-unused space. See better bicycle parking facilities here.

Conclusions

Cary's Design Guidelines Manual is intended to encourage a built environment that works better for cyclists. In some ways it can, but the Manual also includes design recommendations that are operationally undesirable or dangerous for cyclists. Many of these designs have their origins in design practices that were developed by non-cycling engineers and planners decades ago in other communities. Since then, cycling-savvy engineers, planners and cyclist advocates have developed a deeper understanding of best practices for bicycle transportation in the United States. The Cary Design Guidelines Manual should be updated to remove the inappropriate or obsolete design examples and promote better designs that are compatible with best cycling practices.