Effectiveness of Densities for TOD

[Martin]

Has anyone done any research to determine which residential densities around transit stations have the greatest effect on reducing car trips?

We know that a certain minimum density is required to make transit work, but I wonder about TOD plans that put highrises all around the stations. The small households that live in highrises don't generate a lot of car trips wherever they live. By clustering them around transit, we are increasing the average distance between the larger households and transit, and it is these larger households that have the cars and that use them.

I'm not a real estate expert, but families with children, even those for whom access to transit is a priority in choosing their home, aren't likely to want to live next to a cluster of highrise apartment buildings.

Any hard data on how high densities affect modal split, or on how moving closer to transit affects transit use in households of different sizes?

 

[passdoubt]

I think that this is largely a Canadian phenomenon. In the Northeast US at least, development is much more haphazardly clustered around transit links, not nearly as deliberately placed. This is why I'm not sure about your sentiment that single-family homes wouldn't sell near highrises, because I always assumed that the great calculated stratification between them in Canadian suburbs like Pickering was a result of zoning, not market forces.

Regardless, I much prefer mixes that do include single family detached homes within close link to transit. I know my dream in life is to live carless and own a small patch of grass, and that needs to be a reality for transit to be viable.

 

[jresta]

It's really hard to answer this b/c it sounds like you've already answered your own assumptions . . . that i don't think i necessarily agree with. In general i think that access should be the question to answer first and when you feel like you've answere all of those questions then you should move on to transportation.

So to answer your first question -

Has anyone done any research to determine which residential densities around transit stations have the greatest effect on reducing car trips?

Yes, but it depends on what you mean by reducing car trips. Do you mean reducing auto trips to the transit stop? reducing trips to the ultimate destination? or reducing auto trips all together?

We know that a certain minimum density is required to make transit work

I don't "know" this. I can think of plenty of routes that serve suburb to downtown routes that are highly successful that rely almost entirely on parking and/or feeder bus service.

but I wonder about TOD plans that put highrises all around the stations. The small households that live in highrises don't generate a lot of car trips wherever they live. By clustering them around transit, we are increasing the average distance between the larger households and transit, and it is these larger households that have the cars and that use them?

this is almost an aside but i don't understand the fixation with highrises. There's nothing in South Philly over 4 stories (except for 2 hospitals and 2 age-restricted buildings) and we average about 17,000 heads per square mile. When i hear "density" and "highrise" in the same sentence I immediately wonder how much parking they're trying to accomodate. So let's just say you trick out your transit stop with low-rise residential bldgs. in the immediate vicinity and include lots of ground-floor retail. You have a grocery store, a hardware store, a pharmacy, all the daily necessities. Somewhere in your TOD you have a school. People have fewer reasons to leave the neighborhood. I'd also challenge the assumption that large families would make more car trips per person(unless the kids all drive). If most conveniences are within walking distance (most importantly school) i think it'd be fairly even.

I'm not a real estate expert, but families with children, even those for whom access to transit is a priority in choosing their home, aren't likely to want to live next to a cluster of highrise apartment buildings.

i don't think this necessarily true but more importantly i think it's a false dichotomy. As i mentioned before - you don't need height to have density.

Any hard data on how high densities affect modal split, or on how moving closer to transit affects transit use in households of different sizes?

i'll have to dig for it but i'm pretty sure our studies have shown that outside of a 5 minute walk ridership drops by half and by 10% for every minute you add on to the walk.

I think density has little to do with ridership numbers. Cheap ample parking at stations can make up for paltry densities. A strong anchor on the transit line, a vibrant downtown for example, can also make up for a lot.

 

[jresta]

Regardless, I much prefer mixes that do include single family detached homes within close link to transit. I know my dream in life is to live carless and own a small patch of grass, and that needs to be a reality for transit to be viable.

I completely agree, or i did for a while, who knows if i'll move back here or not but . .

my old apartment is the upstairs of the yellow building - a mexican restaurant. The town is 15,000 people in 1.5 square miles - 1/2 square mile is parkland. There are 4 highrises on the edge of town. Otherwise the town is a mix of victorians, twins, bungalows, colonials, a few rowhomes, and very few modern center-hall colonials. The train station is close to the geographic center of town and has 1800 daily boardings.

Every station on the same line with more parking and/or feeder bus routes outperforms this station in terms of daily boards. None of them have highrises within walking distance of the station.

 

[Hipockethipy]

You might like to check out this report, summarising research into traveller's response to the built environment including aspects of land use and site design such as density, proximity to transit etc: http://trb.org/news/blurb_detail.asp?ID=2079

 

[JNL]

Hard data I think you will struggle to find. You may find some useful bits in these (all discuss transit and land use):

How to Make Transit-Oriented Development Work
http://www.marc.org/airquality/2003aqnewstod.htm

Walking as a Local Transport Mode Choice in Adelaide
http://www.dpi.wa.gov.au/walking/pdfs/B13.pdf

If we build it, will they come?
http://www.wsdot.wa.gov/walk/PDF/ProWalk.pdf

Pedestrian Access to Transit: Model of Walk Trips and Their Design and Urban Form Determinants Around Bay Area Rapid Transit Stations, DR Loutzenheiser, Transportation Research Record 1604.

Green Connectors: Off-Shore Examples
http://www.sactaqc.org/Resources/Literature/Bike_Ped/Green_Connectors.htm

CITIES FOR TOMORROW: RESOURCE DOCUMENT, Austroads 1998, comments that little is known about the relationship between land-use location and household travel patterns, and goes on to offers general and policy level concepts for integrating transport and land use. It identifies the issues involved with integrating land use and transport at three different levels, macro (eg. multi-use centres, transport mode, network development), meso (eg. route choice, land use location, local networks), and micro (eg. vehicle speed, environmental capacity, severance).

Hope this helps.