Safety Study of Bicycles on Expressways in Santa Clara County

A study of bicycle-car accidents on Santa Clara County expressways, published by the Mineta Transportation Institute, shows that crossing accidents are greater than all other types of accidents combined. It also shows that shoulders are very safe, with between 0 and 2% of accidents occurring there. Here are details:

• Out of 56 bike-vehicle accidents in the 9-year period of the study on “freeway-like” expressway portions [having few intersections, almost no driveways, and no parked cars; all attributes that increase safety for all modes], 37 (or two-thirds) were “right angle” collisions --especially bicyclists crossing the expressway at intersections. 4 accidents were the “overtake” category. Unfortunately, the details were lacking as to ascertain whether these were motorists running into bicycles on shoulders or acceleration lanes, such as now exists on Montague after County highway engineers eliminated the shoulder for more traffic lanes. However, the worst case ration for "overtake" is 4/56 or 7%.
• Yet for years, as late as September 2005, the repeated argument of County highway engineers and some city traffic engineers was that expressway shoulders are dangerous for bicyclists and/or pedestrians “due to the close proximity of high volume, high speed traffic”. The fact is, the 45 mph speed limit of all expressways locations having prohibitory signs today is less than or equal to that of many arterial roads, and the expressway shoulder facilities are better than those on portions of Java Drive (45), Caribbean Drive (45), Winchester (45), Monterey Road (50) and Trimble Road (50) where there is no sidewalk, no shoulder and no path.
• Source is Table 3-6 of the report Statewide Safety Study of Bicycles and Pedestrians on Freeways, Expressways published September 2001 (which also included other counties.)

Although pedestrians were not studied, I postulate that this same logic and evidence is also applicable to pedestrians walking on shoulders, as follows. Walkers walk in the gutter pan (if that exists) or adjacent to the edge of pavement [see photos], while bicyclists usually ride close to the shoulder line. That's my observation from using expressways since 1967.

Therefore, the bicycle-vehicle collision rate on Santa Clara County expressways can be taken as a worst case for the pedestrians-vehicle collision rate on shoulders of these expressways, for these reasons:
1) walkers are always further removed from vehicle traffic than bicyclists,
2) bicycle handlebars are wider than walkers, and
3) we are ignoring the traffic contention points of intersections and driveways (which are handled separately below, and are not part of staff's claim).

Re intersections:
There is no question that expressway or any wide arterial road intersection area is risky. However, the County is already required to trim shrubs at intersection areas as for bus stops by the County Expressway Plan and earlier. Note: staff's refusal to comply resulted in the 1992 killing of the schoolchild on Capitol. The County Expressway Plan incorporates and makes that statement even stronger.

Re driveways:
Most driveways of expressways are just like a T-intersection with a pork-chop and a yield. A few from before the name change to "... Expressway" are the style for regular arterial roads.

Also see: Expressway topics, links page.