Sunday, April 6, 2014

What makes good bicycle tracks

I have already written here that most bicycle tracks in Tartu are of unacceptable quality.  Too often they are not direct, not smooth, and in places too narrow.  As it seems, the planners do not understand the basic needs of cycling.  Here I explain a little.
Bike track in Aarhus, DK.  It is smooth, and it goes straight across the junction.  The same priority rules apply both for cars and cyclists.
First, safety is important but not all-important.  I have seen claims that safety is almost the sole characteristic of the bicycle traffic. This is simply not true.  Bike tracks are not (just) about safety. They are about a combination of safety, accessibility, smoothness, and speed.  If safety were the all-important requirement, we would never cycle, never walk nor even drive small cars.  But we do.  We accept a low risk of injury if this helps us smoothly to get where we want to go.

Junction of Riia and Raudtee streets.  The bicycle track ends here abruptly at a guardrail (center).  The cyclists are supposed to take a sharp turn right, then left, cross the street at pedestrian speed, and continue on a very narrow sidewalk (right).  It is a safe but very inconvenient solution. A car lane at the same place (left) has neither abrupt turns nor other obstacles.  As the street goes downhill, cyclists can easily achieve speeds here comparable to those of cars.
In order to improve the biking conditions, one must plan the lanes with this suitable combination in mind.  If cycle lanes are very safe but the ride will not be fast and smooth, people will not choose cycling (or choose to cycle elsewhere).  In practice, the picture is complicated by the heterogeneous preferences by cyclists.  Broadly, kids and slow rider prefer safety, fast riders smoothness.  But it is perfectly possible to cater to all of them in most cases.  Usually it is achieved through street hierarchy—slow speed is enough inside a city blocks but large thoroughfares should allow full speed cycling (at least 30km/h).  Cyclists are exactly like motorists from this aspect.
Left: bike track between Maarjamõisa hospitals and University biomedical center.  Except for a few curbstones, this stretch is adequate for short-distance connection inside the university campus.  Due to it's location, it cannot be upgraded for high-speed connection between different parts of the city.  Right: bike track next to a major thoroughfare, Võru street.  Unlike cars, cyclists are supposed to yield at the small sidestreet and take an inconvenient turn just after the junction.  This is a place where the track should be upgraded to allow full-speed cycling.

Second, road users are always interacting and have to adjust to other road users.  This is partly achieved through planning of roads and junctions.  It is important to realize that adjustment is costly, usually involving breaking and speeding up again, and often maneuvering.  Current cycle tracks put too much of these adjustment costs on cyclists.  The tracks almost never go straight across intersections, even at the main thoroughfares, often forcing bikes to slow down to walking speed in order to cross curbstones and take sharp turns.  Second, instead of dedicated bike lanes, cyclists are often expected to ride on pedestrian walkways.  This is an acceptable solution only if these are wide and not crowded.  The most critical points are typically bus stops, turns around street corners, and areas near pedestrian crossings.  Sidewalks in these places are often narrow, visibility low, and many people standing and waiting.  Now compare this with the car lanes at the same stretches.  Those almost always retain their width, there are hardly ever obstacles like curbstones, and they go straight across the junctions.  Most of the the adjustment costs are shifted to cyclists and pedestrians.

Seems like the planners mainly follow two aims: the lanes must be safe, and the motorists should not bear the adjustment costs. Unfortunately, this leads to unusable cycle tracks.