A recent discussion paper (pdf) commissioned by the City of Ottawa for their Downtown Moves Project, produced by engineering firm Delcan, may provide clues of what the Richmond/Adelaide Environmental Assessment may discover about one-way to two-way street conversions. Surprisingly, despite a number of North American mid-sized cities converting their one-way streets to two-way (New York City is the big exception), there is a lack of quantitative evidence demonstrating the effects of the conversion from one-way to two-way operation. In fact, there are strong contra-factual examples where one-way streets have vibrant street life and businesses. Montreal and New York City are two important examples.
Given this lack of evidence and that Ottawa will want to maintain adequate sidewalk width and have dedicated bike lanes on some of these streets with an 18m wide right-of-way, the discussion paper concluded that it work much better to keep the streets as one-way.
The lesson for Toronto, and in particular for Richmond and Adelaide is that if the streets get converted to two-way it will be very difficult to get any sort of bike lanes. Richmond and Adelaide, like most downtown streets are categorized as having 20m rights of way, though the actual width fluctuates.
Highlights of the report
Capacity of one-way streets is higher than two-way:
...one way street can accommodate relatively high traffic volumes with only two (2) travel lanes, given that turning movements can happen from one lane or the other. By comparison, a two-way street will need a wider, three (3) lane cross-section to accommodate a turning lane.
The capacity of one‐way streets can be approximately 10% to 20% greater than that of two‐way streets. Increased capacity can translate into fewer lanes and fewer through streets within a one‐way grid system, or alternatively, the option to reprogram any surplus capacity/space for other purposes (i.e., dedicated parking lanes, bicycle lanes, wider sidewalks).
Though many cities have made the conversion, some notable cities haven't and the streetscape hasn't suffered:
...there are many examples of successful commercial and pedestrian environments within existing one-way street corridors, including in New York City and Montreal. These successes demonstrate that there are likely elements at play other than direction of traffic flow that characterize a successful street such as the width of the roadway, number of travel lanes, width of sidewalks, presence of on-street parking, cycling facilities, access to public transit, the quality of built form and streetscaping along the street, and market conditions.
New York City, NY features a road network that is almost exclusively one-way streets, and it is considered an extremely vibrant pedestrian environment (and New York City achieves the highest transit share in the US).
Also in Montreal, QC, Rue Sainte Catherine and Boulevard de Maisonneuve and others are one-way streets, and are considered very successful commercial streets within the downtown core of the City. In both of these cases, the width of the road, width of sidewalks, presence of on-street parking, access to public transit and most importantly, built form of the buildings on the street, each impact street life far greater than one-way traffic.
The corresponding conclusion is that, on downtown Ottawa 18m wide streets where a dedicated cycling facility is to be provided and sidewalks are to be of appropriate width, this can most readily be accomplished in a one-way vehicular arrangement.
The push for conversion to two-way is coming from an ambition of creating more livable streets downtown. It's an admirable ambition that is shared by the vast majority of people who bike. But it's not clear that two-way conversion is necessary, nor even a sufficient condition for turning Richmond and Adelaide into livable streets (or destinations in the parlance of Vaughan and company). NYC and Montreal are doing just fine with one-way streets. Toronto has plenty of two-way streets that are unfriendly, not just to cyclists, but to pedestrians as well. Dufferin, Jane, Bathurst, Kingston Road and so on.