Data/Follow-up studies of parking after a municipality has allowed 2nd units are difficult to come by. But one common theme ran through (most?) articles on creating ADU ordinances -- parking will be a major issue raised by the public but also a warning that being too strict will only limit the number of legal ADU's... and not the illegal units. Rather, perhaps a compromise in requiring some off-street parking would best address neighbor's concerns and provide a readily achievable/realistic target.
Here's what i could find:
- "As well as being accused of gunning their engines in the quiet of night and racing through the streets (comments made at a recent public forum in Surrey), secondary suite tenants have been blamed for neighborhood parking problems. There is no evidence to support these accusations. In fact, a 1990 City of North Vancouver study revealed that 70% of secondary suite tenants had access to off-street parking. Statistics from Ontario show that residents of single-family dwellings own twice the number of cars as do secondary suite tenants.
- "Parking is a major urban problem because we, as a society, rely far too heavily on automobile transport and lack an extensive, quality public transit system. Urban sprawl and the need to commute due to the concentration of jobs in specific areas contribute significantly to this problem. Parking is an important issue with respect to social planning and public policy; but with respect to secondary suites, it is a red herring." http://www.tenants.bc.ca/ckfinder/userfiles/files/Secondary%20Suites_A%20Call%20for%20Safe%20and%20Legal%20Housing.pdf
- "The potential for parking problems generated by the installation of ADUs is one of the most common concerns expressed by residents. Neighborhood groups are generally opposed to any increases in on-street parking, particularly in areas where competition for existing parking is already a problem, or in neighborhoods where prevailing aesthetic standards make on-street parking less acceptable. Many communities have addressed this issue by requiring a certain number of off-street parking spaces for homes with ADUs. Off-street parking requirements typically range from one to one and one-half off-street spaces per ADU." http://www.mrsc.org/Publications/adu30.pdf
- "Proponents point out that in many instances single-family homes without ADUs could generate just as much traffic and demand for parking as a home with an ADU, particularly in homes with teenage children. They point out that ADUs are often in the homes of "empty nesters," single parents, and single residents, who tend to have fewer cars. Meeting requirements for additional parking spaces could be an expensive proposition for some homeowners and may discourage them from installing an ADU." http://www.mrsc.org/Publications/adu30.pdf
- It should also be noted that one of the benefits of mass transit, TOD: Transit Oriented Development, can also apply to second units. If a property is located within a short distance to major bus stops or other means of transportation, then shouldn't the property be exempt from strict parking regulations -- or at the very least, be allowed to have a reduction in the requirements? Such allowances would be granted to much larger multifamily developments, so it may be appropriate in some cases to apply the same exemption to a single-family, residential neighborhood.
