Classes of bicycle facilities

Yesterday's blog post described the changes in Congress as well as how Rep. Duncan Hunter (R-CA-52) mentioned in an interview about how he felt cycling is more of a recreational rather than a transportation thing. (As a side note, this Rep. Hunter is the successor of long-term and probably better known Rep. Duncan Hunter.)

Yes, it is true that a good deal of cycling is done for recreational purposes. But a good deal of cycling is also done for transportation, due to its convenience and low price, in addition to the built-in exercise. One who rides for transportation gets a workout just by going where one was going anyway. A variety of facilities exist, and facilities can be classified into three classes.


Class I facilities are independent, paved paths 8-12 ft wide that are separated from the rest of the roads. They are typically multi-use and open to cyclists, pedestrians, and all other non-motorized traffic. Standards call for 8 ft in areas with little traffic, 10 ft for typical sections, and 12 ft for especially busy areas. These facilities are popular places to walk and ride, especially for beginning cyclists. They typically run along abandoned rail lines and streams. Often, they're termed greenways, and are considered a form of linear park. An example of such a facility is the Third Creek Greenway in Knoxville.

Generally, these facilities should not be built parallel to roadways, unless action is taken to discourage cycling upon them. The reason is that at every intersection, where car/bike crashes statistically occur most often, there is a conflict between the turning car and the bike proceeding straight. The exception to this rule is in the case where the road has very few intersections with driveways, storefronts, other roads, or anything else. Cyclists can yield at the few remaining intersections. In Knox County, long-term plans call for a greenway paralleling Northshore drive.

Class II facilities are on-street bike lanes (BLs). Useful to have whenever heavy traffic and/or high speeds are present, they provide a part of the road that is set-aside for bicycle traffic. They are also separate from any pedestrian sidewalks that may be present. On a two-way street, they go both ways, and are supposed to be on the right of the rightmost through lane. The delineation of the separate area for cyclists makes all traffic flow more smoothly. These facilities can be built in areas with much turning traffic, since the bike traffic is worked into the traffic stream. BLs are typically 4-5 ft wide. They are typically constructed upon road widening, or upon reconfiguration of existing roads where unneeded car lanes are removed and converted (aka a 4 to 3 road diet). A very popular reconfiguration takes a 4 lane road with two lanes on each side, and turns it into a 3 lane road with one lane going each way, and a dedicated turn lane. The remaining space becomes BLs. Such a road diet has been shown to improve safety and successfully handle traffic volumes up to around 20,000 vehicles per day, especially if there is a substantial fraction of turning vehicles that would otherwise cause delays.

Possible issues with BLs include (1) the problem with parallel parking and car doors opening into the BL (aka door zone), and (2) collection of road debris in BLs. Cyclists riding in the door zone have been killed when opening car doors knocked them into passing traffic. If parallel parking is present, BLs may not be advisable. Currently, experimental setups are being tested with either a "no-go" buffer of 2-3 ft next to the parallel parking, or "bike boulevards" located on the right side of parallel parked cars. Since parallel parking is rarely seen on high-speed roads, it's very possible that there is not a need for BLs whenever parallel parking is present. Road debris needs to be periodically swept in order to keep BLs pleasant places to ride. Recently both Oak Ridge and Farragut completed some new BLs on key streets.

Class III bike facilities are on-street signed bike routes. Signs point to popular destinations such as downtown. Cyclists ride completely integrated into the traffic flow; in many urban areas, cyclist speed and automobile speed are comparable, especially when traffic lights are present. Knoxville is scheduled to have a set of recommended bike routes that have little traffic and low speeds signed this year. Sharrows, or shared-lane arrows, may be placed strategically on streets with a speed limit of 35 mph or less, indicating where in the lane cyclists should ride. On streets with parallel parking, sharrows positioned outside the door zone could be a cheap and preferred treatment. Ultimately, every non-limited-access road should expect to see cyclists and pedestrians, although of course some roads are safer and friendlier than others.

Back to transportation, the different types of facilities have differing levels of usefulness. Class I facilities are useful in linking spread-out locations, but are extremely limited in terms of handling traffic within an urban or suburban area. There simply is not the space to superimpose such a network on top of most built-up places. Class II facilities are good for built-up heavily traveled roads, and can connect a plethora of destinations. Class III facilities are part of the existing road network with perhaps small tweaks to facilitate cycling. When one considers how a mediocre cyclist can travel around 10-15 mph, and how distances traveled per trip are typically only a few miles each, cycling can be an effective form of transportation. The top cycling cities of the US (Boulder, CO; Portland, OR; and Davis, CA) bear this fact out with their substantial percentages (5+%) of trips taken by bike.