Horses come by my place in toronto fairly regularly, as I happen to live close to the OPP's training stables (and I think the Toronto Police stables as well). They are not much of a problem when cycling, but they are difficult to manouver around in a car. Of course police horses are trained to deal with traffic and crowds and do not scare easily.

To the original point - if we pursue a policy of urban intensification, coupled with parking-free housing, we might see 25% or more cyclists in some corridors and neighbourhoods. In some cases specific facilities might make sense (see st george street/beverly street bike lane), and moves could be made to make HPT corridors more efficient (in Toronto - adding lights where the belt line crosses Bathurst and Avenue roads would make sense). Calgary has actually spent a lot of cash on it's HPT corridor, with bridges and snowclearing that are more efficient than their automotive counterparts.

In most cases, the smaller footprint of bikes vs. cars will likely mean that on already congested routes, a greater proportion of cyclists will markedly increase average car speeds. This is especially easy to see at lighted intersections - way more bikes get through a light cycle than cars do - massively increasing the amount of vehicles clearing a light cycle. In any case where cars wait for two or more light cycles to cross, an increase in cyclists will reduce their wait times almost proportionately.

However, given our society's particular characteristics, I expect that we will see 25% or more trips by walking before we see that proportion of people cycling. It is already the case that a large number drivers to the UofCalgary walk several km each day from the McMahon Stadium parking lot - it seems that walking (even during prairie winters) as a more viable option than public transportation (which would decrease the walk for these individuals at the university end by about 75% or more).

In Ottawa's survey, 7.5% of commuters walk to work - in a city with a notoriously harsh climate (of National capitals only Moscow is colder). In some Ottawa neighbourhoods the walk to work rate reaches 25%.

In terms of sharing facilities, motorists will eventually understand that it is absolutely easier to get past a pedestrian, a cyclist, a scooter, or a motorcycle than it is to pass another automobile.

I am not of the opinion that people are unable to appreciate that hundreds of pedestrians can cross a street during a 2 minute light cycle compared to a few dozen cars.

To the original point - as the non-automobile fraction increases in a particular area, the preexisting roads and intersections will see less congestion and faster average speeds - reducing the demand in general for cycling-only facilites.

That being said, I'm sure some stripes may be added given particular circumstances, some streets might be closed to automotive traffic at various times of the day, and some bike only facilities will be seen as efficient, but the general rule will be less need as cars decrease in proportion rather than an increase.