Siamak... I could not find Prof. Schimek's report. But here is what I have learned. With regard to intersections, about 1/3 of bike accidents occur at intersections, and they account for about 2/3s of fatalities. Conversely about 2/3rds occur at non-intersection locations. (See 2005 NHTSA Statistics.)

I could not find any data that proved or disproved the hypotheis that bike paths are more or less safe, but data and sample sizes are a problem. Most of the research admits that the historical data has not accurately distinquished between bike paths and bike lanes. One researcher anecdotally points out that a major problem with bike lanes is that they are the recipients of road debris and are not scrubbed clean by auto traffic action---standing water, mud, pine needles, leaves, etc. and are therefore frequently departed from or avoided by bikers. (Forester 1983, footnotes discussing bike lanes in the San Francisco Bay Area)

Again there is limited data but one study suggested that lane-width for auto traffic was relevant and that directionally they observed fewer bike accidents occurred when the width was at least 10 feet. (City of Orlando, FL)

Another study indicated that major causes of bike accidents were hazards that could not be readily seen or seen by the rider too late--pot holes, sand, stones, etc. (Multiple studies)

Finally, another significant cause is when riders look over the shoulder to scan behind them resulting in swerving either off the pavement or into a car. Sometimes they swerve off the pavement but lurch back into the road. (Multiple studies)

It's seems pretty fair to conclude that separating bikes and cars is a desirable thing to do. However, part of the neglible-safety argument for bike paths is primarily based on the fact that they are typically bi-dectional (two-way) and shared with pedestrians and opposing bike traffic. This is a cause of significant bike path accidents and injury. In Minneapolis, virtually all of the bike and roller skate paths around the lakes are one-way.

Finally, I would like to point out half in jest, and half seriously that we have been attracting more horses to Chappaquiddick roads and their shoes would likely adversely affect the surfaces of bike paths if permitted to use them. Moreover they are likely to present a road hazard to bikes ignored by all studies. The riders do not equip them with diapers nor feel responsible for picking up after them. Is there something that I understand that mandates certain human behavior as it applies to canines that does not apply to equines? 

Frank J. Partel, Jr.