GEOG 346, Day 10Condon: Chapter 3 – Design an Interconnected Street System

Housekeeping Items• We’ll continue for a little while in groups on the mapping

exercise (enhancing alternative transportation options for Nanaimo). One thing I should have clarified last week – you don’t need to write up any text. The colours and markings you make on the Mylar will indicate your intentions – for instance, corridors for express buses, trams or LRTs. You should have a key on your map to explain what the colours and markings mean. Then, when each group briefly reports back to class, you can explain what you came up with.

• The film, “Biophilic Design,” is now available for viewing at the Library Reserve Desk.

• Two very good films were shown as part of International Development Week on Tuesday night: “Food Security: The Future is in Your Hands” and “Voices of the River.”

Source: BC Transit; figures for 2001

Recent RFP for Nanaimo RegionThe primary trip purposes of interest consist of (origin or destination trip purposes):• Work (including during)• Post-secondary school• Grade school• Dining/restaurant• Recreational/social• Shopping• Personal business (e.g. banking, doctor, etc.)• Go home (destination)• To pick-up• Drop-off or chauffeur, etc.Some of these trip purposes are "chained.“

Trip ModeA trip consists of the use of one or more travel modes.• Automobile driver• Automobile passenger• Truck driver• Transit bus (including route numbers)• handyDART• School bus• Other bus• Taxi/Airport shuttle• Bicycle / Roller blade• Walked part way• Walked all the way• Electric (motorized) wheelchairs• Other

Trip Origin and Destination and Land Uses• House or apartment• Office building• Industrial• School• Daycare• Hospital or medical• Store, restaurant or theatre• Religious institution• Other services• Farm or vineyard• Indoor recreational (i.e. gym)• Outdoor recreational (i.e. park, beach, golf course)• Airport, long-distance bus depot, etc.• Ferry terminal

Study Area / Administrative Areas

We will do our own analysis of street connectivity, using 3 neighbourhoods in Nanaimo

Agenda for Today• Finish up remaining three reports on

how to improve transit in Nanaimo.• Old-fashioned neighbourhoods tend

to have laneways whereas subdivisions usually don’t. Their benefits are said to include the following (these are cited by Condon as well): avoidance of ‘snout houses,’ avoidance of interference with pedestrians and on-street parking because of the number of driveways, and access for utilities and delivery vehicles. [See also www.cityofchicago.org/city/en/depts/cdot/provdrs/alley/svcs/green_alleys.html.]

• Review Chapter 3 and then introduce an exercise for next week.

Source: Boston Globe.

“Snout-fronted” houses

Chapter 3• p. 39- “Street systems either maximize connectivity or frustrate

it.” • Condon claims that, prior to 1950, North American neighbour-

hoods were rich in connectivity. Then the paradigm changed. Today over 60% of the urban landscape takes the form of a dendritic (or tree-like) street system.

 

Comparison of Street Layouts (Source: http://www.fhwa.dot.gov/publications/research/safety/pedbike/05085/chapt6.cfm)

Street Design Standard New Urbanism

Basic layout Dendritic Interconnected grid

Alleys Often discouraged Encouraged

Design speed Typically 40–48 km/h (25–30mi/h) Typically 32 km/h (20 mi/h)

Street width Generally wider Generally narrower

Curb radii Selected to ensure in–lane turning Selected for pedestrian crossing times and vehicle types

Intersection geometry Designed for efficiency, safety, vehicular speed Designed to discourage through traffic, for safety

Trees, landscaping Strictly controlled Encouraged

Street lights Fewer, tall, efficient luminaries More, shorter, closely spaced lamps

Sidewalks 1.2 m (4 ft) minimum width, outside right–of–way to undulate

1.5 m (5 ft) minimum, with right–of–way and parallel to street

Building setbacks 4.5 m (15 ft) or more No minimum

Parking Off–street preferred On–street encouraged

Trip generation Developed from a sum of the users Developed from a reduced need for vehicular trips

Chapter 3• Traditional grid patterns feature 2-3 different types

of streets: streetcar arterials, residential streets, and sometimes laneways.

• Dendritic systems have trunks (freeways or minor highways) major branches (major arterials), minor branches (collector streets), and residential streets and cul-de-sacs (twigs and tips).

• What are the strengths and weaknesses of each of these road networks?

• Condon, on pp. 41-42, lays out the difficulty of attempting to challenge in practice the still largely prevailing approach to road planning.

Chapter 3• One disadvantage of

dendritic patterns is that people drive 40% more, produce 40% more GHGs, and possibly more as households may often need an extra car.

• It has been common practice to widen major intersections, as these tend to be chokepoints, and these became convenient for cars, but challenging for people with mobility issues.

Source: http://www.fhwa.dot.gov/publications/research/safety/pedbike/05085/chapt11.cfm

Chapter 3• The disparities can be seen in the following

figures: per 100 million miles travelled, there are .75 fatalities for transit riders, 1.3 for drivers/ passengers, and 20.1 for pedestrians.

• Suburban streets and arterials, especially, have less “side friction” than most traditional streets, with the result that cars are speeding faster. Pedestrian deaths are four times more common on wide suburban streets than urban arterials. A car travelling at 35 mph is ten times more likely to kill a pedestrian than one travelling at 25 mph.

• What is side friction and what causes it?• He cites an example Broadway Avenue in

Vancouver: 4 through lanes, 2 parking lanes that become through lanes at rush hour, and no separate turning lanes (for the most part).

Chapter 3• In Vancouver, streetcar arterials average

about ½ a mile apart, which encourages people to walk to transit.

• Even in traditional single-family urban neighbourhoods there is a lot of ‘hidden’ density that supports transit use – for instance, duplexes, secondary suites, and laneway units. He notes that densities are often as high as 17 units per gross acre (inclusive of streets), which is above the threshold for transit.

• The curvy pattern and low densities of suburban neighbourhoods make them challenging for transit, not the least reason being that bus stops must often be far away from homes (see Figures 3.2 and 3.3).

Chapter 3• Wide suburban streets are not only not safer for pedestrians,

they have not shown any improvements in terms of fire safety and other forms of emergency response. What they gain in speed, they lose in directness (see the information on pp. 56-58).

Chapter 3• In traditional urban

neighbourhoods, unless there is advanced gentrifi-cation, the streetcar arterials will support smaller-scale retail, whereas in suburban environments retail tends to be dominated by chains and big-box stores that stake out major intersection and high traffic areas, in addition to destination malls and strip malls.

Chapter 3• While cul-de-sacs are pleasant for

those who live on them, typically only 25% of those living in a subdivision enjoy this pleasure. Suburban layouts also lend themselves to being gated communities.

• Another trend in street design is the use of superblocks (40 acres or more in size). When poor neighbourhoods in NYC and elsewhere were bulldozed to create ‘housing projects,’ the streets were bulldozed along with them and replaced with super-blocks. These had some associated social problems. Do you know what they were?

Jacob Riis Housing Projects (NYC)

Different Varieties of Grid

• Condon talks about the different varieties of grids that are possible, including differences in block sizes.

• Not only does he favour grid systems over dendritic, he is a fan of the Vancouver and Seattle system of blocks which are 640’ wide and 320’ deep, and which typically feature lots that are 33’ wide and 110’ deep (5 acres). Portland, by contrast, has blocks that 200’ on each side (<1 acre), and Manhattan has blocks that are long and skinny (900’ by 264’).

• He feels that Vancouver blocks are adaptable to a variety of different land uses and building types (see pp. 52-53).

Taxicab geometry versus Euclidean distance: In taxicab geometry all three pictured lines (red, yellow, and blue) have the same length (12) for the same route. In Euclidean geometry, the green line has length 6×√2 ≈ 8.48, and is the unique shortest path.

Source: Wikipedia

A one square km superblock sector in Milton Keynes framed by major roads on a grid configuration. The road network within the sector uses cul-de-sac streets complemented by bike and foot paths which connect the entire sector and beyond

Street Patterns• p. 54- “No single feature of sustainable community design is

more important than road width.” And, one might add, street pattern. It affects how much people drive and how much GHGs they emit. While suburbanites reduced kms. driven during the oil price spike, they did not decrease their automobile dependence. On the other hand, residents of traditional neighbourhoods actually took transit considerably more.

• Nonetheless, despite this, there is considerable resistance from developers because of loss of developable land and added cost. In the past, developers were required to extend the existing grid when developing greenfield sites. Today, they are tasked with creating their own internal road network adjacent to the nearest arterial, though there may be guidelines.

• Nonetheless, alternative standards and traffic calming are making inroads. For examples of many different approaches taken in Vancouver, see http://www.cremtl.qc.ca/fichiers-cre/files/TrafficCalminginVancouver.pdf.

Street Patterns• p. 65 – “Of all the challenges presented in this book,

getting the street system right may be the most daunting.” Given that dendritic patterns are so prevalent, how do we change those or adapt them? Will future subdivision dwellers be “stuck up a cul-de-sac in a cement SUV,” as James Howard Kunstler suggests?

• One tool at our disposable is software that helps people to envision how their streets can be transformed into something much more pleasant. Distributed by the Sierra Club, “Community Transformations” uses a sophisticated form of Photoshop to create before and after pictures – see http://www.sierraclub.org/sprawl/community/transformations/14thst.asp.