Monday, September 29, 2014

Hedgehog Concept

A couple of years back, read ‘Good To Great’, and was really struck by the idea of the hedgehog principle. And I asked myself “What am I the best in the world at?”, and realized it was finding out about things. Not knowing things—other people are better at being experts at things than I am. But give me something no one knows very much about, and I’m golden. One of the reasons I’m in academia right now (rather than consulting) is that it gives me time to ‘Do the reading’. And that’s most of what I do—read on a wide variety of topics, and report back. So, ask anything—even if I can’t answer you today, odds are I can give you an answer shortly.

Friday, September 12, 2014

Downtown Streetcar

Don't know how closely you've been following the downtown streetcar. SLC wants to run it up the hill from downtown to the U, but can't decide how. S. Temple, 100 S., and 200 S. have all been mooted. 

Might be a nice place to recommend a study to them, talking traffic impacts, comparing the 3. 

Part of the deal is they want to talk future expansion to the north part of the U, which is currently a long walk (4+ blocks) from TRAX). Almost certainly along North Campus drive, 200 S. doesn't permit it. The U is currently running an express shuttle along the route.

Wednesday, September 10, 2014

Lyft, Uber, and Taxi

Visiting the Dominican Republic, one of the most impressive things were the share ride taxis. Ever so much more frequent then buses, even if they were more than a bit cramped...always made me wonder 'Why no private transit?'.

However, the furor Lyft and Uber are facing, as they compete with traditional taxis, it suddenly makes sense. In Utah, the taxis are often owned by their drivers, and represent both a considerable investment and their livelihood. I asked a driver, last night, what he thought of it. He considered it a disaster, that making a living driving a taxi was hard enough without the added competition. He noted that to do so "You practically have to live in your car".

But I've also been in a yellow cab, as the dispatcher called out, over open broadcast radio, the names of the next taxi in the queue, due to pick up a ride. Regardless of the location of the taxi, the location of the fare. Every driver gets a fare, in the order which they have declared themselves available. Equitable, but brutally inefficient. For the driver, never a chance to grab a bite to eat, or use the bathroom--their name might be called. There is never any indication of how long the queue is. Nor is it fair to the driver--you get A fare, but their is never any indication of how good a fare it will be. The use of a human dispatcher alone, reading off a clipboard, given the enormous advances made in information technology, was appalling.

And for someone waiting on a pickup, it's misery. You have no idea when your taxi will arrive. Nor that it will pick you up when it does. I've had taxis, unable to find me within the first minute, simply take someone who hailed them. (And in fairness, I've also stepped into taxis that someone else called for).

Part of the reason for the inefficiencies of taxis have to do with the Faustian bargain they have made. Cities need taxis--they are an essential part of transportation infrastructure, especially for business travelers, providing someone who doesn't know how to get around, or where they are going, with a way to do so. In effect, on-demand car hire. But to ensure enough cabs to provide this service, the city must ensure that the cab owners have an incentive to own, maintain, and operate their own cabs. Typically, this is done by limiting the number of cabs, so that all registered cabs must have a 'medallion'. In New York city, where no medallions are being issued, the price for a medallion is over a million dollars--for the right to drive a cab in NYC, you pay a million dollars. And then hope you can pay it off, by driving that cab. 'Gypsy' cabs exist for a reason...

In a more equitable and more humane world, dispatch would be automated, or largely so. Largely, it would be done with a smart phone app, which would map the locations of both cabs and fares.

The second part of the Faustian bargain is the requirement to take any and all fares, regardless of destination. A trip with no possible return fare is known as a 'dead-head'. In effect, the taxi must drive twice the distance--to get the fare to the destination, and then to get back to a central location where fares are more available.

In NYC, there was a furor when gas prices first spiked, as cabs began to refuse fares to the outlying boroughs, which combined long trips with not possibility of a return fare. The price per mile being offered was unequal to the cost per mile required.

The fare cannot vary with costs (which vary with gas prices). It also means that the fair is never perceived as fair. If the rate is too low, the drivers make too little money. If the rate is too high, the public feels they are being gouged.

The third part of the Faustian bargain is the fixed fare--it costs the same to go anyplace. Flag drop plus a mileage rate, with both fixed, regardless of market demand. It puts both a 'floor' and a 'ceiling', on the price. The pricing is static, where dynamic pricing is far more efficient. Nor are different cabs (or cab companies) allowed to charge different rates.

In a nutshell, no one is ever happy with the arrangement--neither drivers nor regulators, nor users. 

In this mess, Lyft and Uber have stepped.  The difference is the lack of the Faustian Bargain. 

They are, in effect, gypsy cabs, with Lyft and Uber providing dispatching services. Pricing is dynamic, set by whatever the driver will accept. As demand rises, so do the fares. And as fares rise, more people are willing to drive, so there is more supply. Ie, a market instead of a Faustian Bargain.

I expect that the 'long-range dead-head' customers are finding themselves paying much more. Which, given that they are receiving much more service, seems like a fair fare.

Monday, September 8, 2014

Big Data comes to transit

Check out Bridj, a new ride sharing service, using multi-passenger vans.

Cell phones have made wealth of geolocation data available. For decades, transit planning has relied on a mix of rules of thumb (population/jobs within a half mile) and empirical experimentation to determine where routes should be established...but now that can change.

Tuesday, September 2, 2014

The Bureaucrats answer vs. the Engineers answer.

This is simple enraging.
It is the bureaucrats answers: "It can't be done because it will require additional resources", rather than the engineers answer: "It can be done, but it will cost..." It would cost. No questions asked. And if the costs can't be paid by the users (through fares) they would have to be paid through other means. For UTA, that means taxes.

"How can we get more money?" is not a bad question. It is a critical question. Because money is the critical input for services. If you want to provide more services, you need to get more money.

Efficiency is a certainly a laudable goal. Asking "How can we provide the most service, the best service, for a given amount of money?" is important for any organization. But it is not necessarily the primary question that a transportation agency should be asking. It is not the question UDOT asks. UDOT asks "What are our needs?" and then goes looking of ways to fund them. It is a growth mentality, a mentality responsive not only to current conditions, but to future conditions.

Saying 'Can't be done' implies that it can never be done. The long range plan is full of projects that are impossible, today. But they are projects that are possible, over time. That's why its a plan--a list of future actions to meet a future objective. Achieving things, over time, that cannot be achieved immediately.

Thursday, August 21, 2014

Phil Emmi Joins Outlook Tower Blog

My name is Phil Emmi. I'm a professor of urban planning. Matt Miller invited me to join in on his blog. Let's see what happens.

Wednesday, May 21, 2014

Housing Affordabilty

The effect of increasing H+T costs is compounded by tenure type. Housing affordability issues are most severe in locations where renting is the primary form of tenure. Renters, unlike owners, are not insulated against increases in housing costs. Rental tenure in America is characterized by short leases, so increases in property value can rapidly be capitalized into higher rents. Rising rents increase housing costs, resulting in the displacement of previous tenants, who are no longer able to afford the higher rents. In contrast, mortgage payments are fixed upon purchase, so that current homeowners are largely insulated from the effects of increases in housing costs. The primary cause of declining affordability for existing homeowners is increasing property taxes, of which homeowners pay only a fraction of the increase in value.

The percent of homeowners also acts to confound actual housing affordability conditions. In the past decade, the appreciation in home value has outstripped appreciation in wages so that many current homeowners could no longer afford to buy their own homes. While they are affordable for the current owners, their appreciated value makes them less affordable to prospective owners. Over time, this compounds housing affordability issues. Lower housing affordability means that fewer households are able to become home owners, and must remain renters. They thus remain vulnerable to further increases in housing costs. As rents rise, so does the premium associated with home ownership, so that households are willing to pay more for property. 

Cities with high monthly rents also have high property prices for a reason.
Policy intervention is necessary to ensure that housing locations near transit stations remain affordable. Without measures to maintain housing affordability, areas around transit stations will see the displacement of low-income renters in favor of medium income owners. There is a strong negative relationship between income and transit ridership, as low income households are more likely to be transit dependent, so this process acts to reduce transit ridership. Changes in the distribution of tenure will also reduce the benefits of self-selection. Household locating near transit self-select for proximity to transit, and are thus the types of households most likely to make use of transit.

Over time, as household characteristics, such as place of work and size of household change, the utility of proximity to transit changes. A single person household is extremely likely to be able to make use of transit, while a two-worker family household is less likely to be able to do so. Unable to make use of transit, such households would then require multiple vehicles, resulting in transportation costs in line with the metropolitan norm. In a worst case scenario, housing units around transit stations are owned by non-transit using households and yet suffer from higher average housing costs. In contrast, households in rental tenure are more likely to relocate in response to changing conditions, so that even if housing costs rise, transit ridership suffers less.

Long term, ensuring a supply of affordable transit oriented housing near stations will require policy intervention. The amount of affordable housing that is constructed is minimal. Most affordable housing results from the depreciation of former medium income housing. Constructing new housing as infill development requires higher density housing than the surrounding urban fabric, because the land value has increased in the interval since the initial development of the area. Constructing new affordable housing requires higher densities, due to the lower return per unit. In combination with parking requirements, new affordable housing is required to ‘go vertical’ to achieve sufficient density.

Reducing or eliminating parking minimums near transit stations would be an effective policy. Reduced parking would reduce per-unit cost of new affordable housing, and reduce the tendency to convert affordable transit oriented rental units to unaffordable transit indifferent owner-occupied units.

Friday, March 21, 2014

Nice Density

What you see in Regent Street now is a 1910 rebuild of the Nash from 1810. Along the edges of  Regent’s Park, you have these big, long terraces designed like palaces, so the wealthy people in the row houses could feel like they were living in a wing of  Versailles. Then, behind that, there are tiny curving streets with modest houses for those days, which were intended for middle-class people.

This is a lesson how do to do density nicely.  

Good urbanism requires density

Pushing density an article of planning dogma. 

...with vehement NIMBY opposition.

Many dense places are slums.


-'The Projects'

Not because of density, because of age.

'Todays mass market housing is tomorrows affordable housing'

--Inner ring suburbs: SSL, South Ogden.


Myth: Higher density requires multi-story.

Reality: Requirement created by parking requirements.

'9 acres of of land: 8 acres of parking'

Yet there is lot of existing higher density. How?

  • On-street parking

  • Small blocks

  • Multi-family on the corners

Monday, March 10, 2014

'Houses like Palaces'

What you see in Regent Street now is a 1910 rebuild of the Nash from 1810. Along the edges of  Regent’s Park, you have these big, long terraces designed like palaces, so the wealthy people in the row houses could feel like they were living in a wing of  Versailles. Then, behind that, there are tiny curving streets with modest houses for those days, which were intended for middle-class people.
Funny to think of multi-family that way. But a good way to think about residence in someplace beautiful, with a unified sense of design. Not a whole city built in one design style, but a community with a unified esthetic, rather than one of ticky-tacky takes on 'romanesque' and 'cottage' on an ad hoc basis. Part of the reasons suburbia needs such wide distances between houses is that the styles are so clashing.

Friday, March 7, 2014

Wednesday, March 5, 2014


Got to figure out how to do this for SLC.

Also suggests the use of GTFS feed data for mapping bus speeds, and determining where buses are the slowest. If buses are stopping too often, good candidates for removing stops. If buses are stuck in traffic, good candidates for dedicated lanes.

Monday, March 3, 2014

From Human Transit:

  Ridership at different times of day is interdependent, if only for the obvious reason that most transit trips are round trips.  If you cut service and thus reject a customer at one time of day, you'll likely lose their business in the other direction as well.  The most obvious "time of low demand," the late evening, is also a "guaranteed ride home," which means it affects the overall attractiveness of the product. 
More important, a consistent pattern of all-day service (including "times of low demand") is a powerful tool for..<making low vehicle ownership possible>  That's is why many transit agencies are now committing to a policy "Frequent Network" that guarantees service over a certain span regardless of trip-by-trip ridership.
And from the comments:
It is hard to build up a transit system when most people only look up on it as a necessary evil for the "less fortunate." For a transit system to be useful it has to run when and where it might be needed and not just when it can maximize revenue. Since most transit line recover less than 50% of their cost from the fare box it is probably perceived to be an advantage to run the minimal possible service rather than try to build up ridership to maximize benefit.

Human Transit continues to be profoundly thoughtful about transit.

Provo fumbles on BRT

Provo has dropped the ball on BRT.

Full out NIMBY attack force, and the Provo City Council quails, flails, and crumbles.

The Federal Funding is contingent on project quality. By eliminating dedicated lanes, and eliminating two major stops, Provo has seriously impaired it's capacity to complete for funding. It has cast serious doubts on its own commitment to the project. They've certainly and now with the closure screwed around long enough. The project has been in process for 15 years. If they wait too long, their environmental documents will expire, and they will have to start again from scratch.

A major regional transportation project should not be held hostage by a handful of people.

Lines like this drive me mad: "It's a cultural change where people are willing to give up their cars for mass transit". No one is coming to take their cars away. No one has to give up their cars. Transit makes it possible to drive less. POSSIBLE. Not mandatory!

Surprisingly thoughtful article from UVU student paper.
Nice to see not everyone is off their rocker.

City of Provo documentation for before can be seen here.
The level of analysis is clearly intense. This project has been studied to death. Concessions that significantly impair the quality of the project have already been made.
However, despite these significant changes to the project, many residents living east of 900 East still remain opposed to the 900 East alignment, and have proposed a new alignment
If you aren't prepared to trust what your consultant tells you, don't hire one. The are incredibly expensive. As is, they are already in preliminary engineering, paying money to have the facility designed, when they have not even formally agreed on the route!

Alternatives proposed by NIMBY residents are typically to the sole benefit of those residents, to the detriment of all other stakeholders.
ProvoBuzz talks about the new 'Route 0' in balanced terms.

A ways back, the LRTP proposed extending TRAX south into Orem. At the time, it seemed insane. But with the Provo portion of the BRT so unstable, other alternatives need to be considered.
But it seems ProvoBuzz has the full, sordid backstory...1999 visioning study, 2005 Alternatives Analysis by Carter Burgess...then proceeding to a full EA, lasting from 2007-2011. Which, to me, is a big red flag. An EA should take about half that long.

BYU sends up another red flag, by failure to yield ROW. Donating ROW (in lieu of cash) is the transit planning version of putting your money where your mouth is. 
  The transit planners’ initial preferred alignment was to take BRT across the BYU Campus on East Campus and North Campus Drives, but because these were privately owned streets, the University would need to grant a permanent easement and allow improvements to be made for stations.  BYU declined to give permission, which led to the option of moving the alignment to 900 East during the EA process.
Nor was BYU alone in such behavior. Provo kept shifting its preferred alternative, from 100 West to University Avenue.

Extremely notable in all these articles is the lack of maps. Does no one know how to make maps? But that may be deliberate--maps are specific. They tell you exactly where things are located in space.

I find this unbelievably:
 Because the City is not a project sponsor and has no financial obligation to the project, the Municipal Council’s recommendations are not binding on UTA; they simply express whether or not there is local support for any given alignment. 
First, I'm scandalized the Provo isn't kicking in any money. Any city getting the benefit of a fixed guideway transit facility needs to put in its pound of flesh. Secondly, the lack of non-binding resolutions means that the Provo city council is dodging any accountability for decisions made. 

Details here

And maps! Beautiful maps!

Monday, February 24, 2014

Tour-based models and Walking

Only recently have travel models advanced to tour based models that recognize that all trips are not made from the home, but that people 'run errands', and combine several trips into a single tour. This has implications not only for automobiles but for all modes.

Every trip begins and ends with a walk. It is not always a very long walk, but it always exists. Every transit trips begins with a walk to the station/stop. And ends with a walk from the station/stop to the final destination. For automobiles, the initial walk distances is typically very short, as most people park closely to where they live. But the walk after parking, across the parking lot, or out of the parking garage, may be quite long. In both cases, the portion of trip spent in-vehicle is only part of the journey.

It would be better if each portion of that journey was considered a trip on a tour. Transportation models ought to consider pedestrian trips, and pedestrian scale transportation networks will require further developments in this area. Considering only the in-vehicle time ignores the significance of the walking portion of these trips, and the significance of the walking environment.

Much of the research on roads is on the effect of pavement quality on travel speed. There should likewise be extensive research on the effects of the quality of the pedestrian environment on both the likeliness to walk and the distances walked. This research will have two strands: The first geometric, measuring network qualities such as connectedness and the directness of paths through the network; the second qualitative, measuring the quality of the travel path.

Secondly, for development considerations, it would be better to consider each portion of the trip (Walk, Vehicle, Walk) as a separate trip. Specifically for purposes of retail gravitation. If the vehicle access point (station/stop/garage) is a trip end, then centers where a greater number of trip ends concentrate should be more attractive. Where someone catches a train (or keeps their car) may vary by virtue of what else is there.

Friday, February 21, 2014

Attached Housing, Detached Garages?

In January, I visited my friend near Washington, DC, where he owns a very expensive house. It was not a small house, but it was an attached house. But it was a very well designed attached house. With a detached garage, which was attached to other garages.

It is easy to forget that the Ranch or Rambler house of American suburbia was (in its time) quite an innovation. Historically, most garages were not attached. For the narrow and deep lots of streetcar America, it was impossibility. So most garages were alley access to the rear, and many were little more than sheds.  Putting the garage and house under a single roof was quite an innovation.

In most of America, attached housing still labors under a stigma. It is still second-class housing, for people unable to afford better. But I wonder--would more people accept attached garages? Were a developer to detach garages from houses, and then attach the garages, would the result be a saleable product?

Perhaps. But it would have to be well designed, and designed in such a way to reduce the amount of land area devoted to roads. The size of an average two-car garage is 400 SF. Detaching them from houses and aggregating them doesn't change the actual number of SF of ground area used. The size of an average two-car garage is 400 SF. Detaching them from houses and aggregating them doesn't change the actual number of SF of ground area used.

There is a reason that apartments have parking lots rather than individual garages. Rather than having individual driveways accessing individual parking lots, there is a single driveway accessing multiple parking lots. But that also constitutes a loss of square feet to the owners--a driveway is still usable living space.

To make it work, the garage clusters would need to be peripheral, located on the edge of the development. Yet to maintain the garages as personal and private space they would need to by connected to the homes. This suggests a cul-de-sak format, with garages arranged around a bulb that has ready access to the roadway.

Not an attractive urban pattern. And thus not an efficient development pattern.

Shout out: BusNinja


Monday, February 17, 2014

More Marchetti's Constant


"Why we're reaching our limits as a one-hour city"

Specifically, I was struck by this paragraph:
The one-hour-wide city, in Sydney, is reaching its limits. A city that has got 20 people a hectare and 40 kilometres an hour will become dysfunctional after about 2.5 million people.
One of the topics I'm very interested in is who gets rail--how big (and how dense) does a metro area have to be before it gets rail? (Or equivalent fixed-guideway transit).

My prior 'rule of thumb' has been about 2 million people. I would be VERY interested to see where (and how) the author arrives at that number. The author, Peter Newman, is a professor of Sustainability in Australia, who popularized the term 'automobile dependence' and write a highly cited book about it.

Friday, February 14, 2014

Marchetti's Constant

Reading about Marchetti's constant today, which suggests that all humans strongly prefer to spend about an hour a day in travel. (Half hour in, half hour out). This supposedly holds across all cultures, in all contexts.
Walking about 5 km/hr, and returning back to the cave far the night, gives a territory radius of about 2.5 km and an area of about 20 km^2.
20 km^2 is about 5000 acres. Conveniently, Salt Lake City's blocks are about 10 acres, so I have a ready conversion metric, so that means 500 blocks, which is a gird 22 blocks on a side. #

This range supposedly applies to villages with agricultural fields and the area contained within the outer walls of ancient cities. This implies that it applies to modern cities as well, or rather the walkable portions of them. Which implies a size limit for Transit Oriented Developments as well. Given a half hour time budget for commuting, of which at least some is taken up by the transit trip itself (say half). This suggests that a 10 minute walk*** to a transit station may actually be more appropriate. Indeed, Calthorpe's original TOD concept* had a 10 minute walk to a heavy rail, from a max distance of about 2000'.

This suggests that the 'Density Gradiant' near transit stations should be an extremely steep one, with elevator apartments (3+ stories) adjacent, and single family homes a half mile away. Because people beyond that half mile aren't likely to walk to the station*.

TOD (Transit Oriented Development) is frequently done badly. Largely because we lack these metrics. If TOD is going to work, the majority of residential units have to be next to the station. Not behind the parking lot, not beyond a belt of adjacent commercial development. Right next to it. Let the Park&Riders walk through that access path to the station. Direct them down a single avenue, running the gauntlet of convenience retail every day. Done right, ground-floor retail could actually be made to work, and in  way that inconveniences the minimum number of apartment dwellers.

In a way, NAM** does us a bad turn. The idea was for transit oriented metropolis, with independent cities clustered around transit stations. Each with their own 'neighborhood center' core. of retail and office development. Nothing like that has ever been built. A 'Transit Metropolis', where transit is embedded in the urban fabric, would look very different.

Recall that most 'New Urbanism'**** is greenfield development, not infill. Even if we fix the street connectivity and raise the density, any given metro area has less than 50 transit stations. 50 possible TODs, each with about 288 acres within 2000' of the station. Some tiny fraction of the total urban area.

*Certainly, some will, but they will be the fast walkers: Young, able, athletic.  Biking to station probably occurs from outside the half mile circle. Presuming a bike to travel 3 times as fast as a walker, say the 'Bike Zone' extends out to 1.5 miles.
**The Next American Metropolis
***People coming from longer distances walk faster. I stroll at about 3.0 miles per hour, and race-walk at about 4.0 miles per hour.
**** AKA 'New Suburbanism'

#How big can a CBD (Central Business District) get before it is 'too big'? It can't scale in size to population, certainly.

The paper is happily available online here

Wednesday, February 12, 2014

Bus Stop Location

Two issues concerning bus stops: 1) Their location; 2) Bus bulbouts

Bus stops on the far side of an intersection are superior to buses on the near side of an intersection. There is a naive belief that a bus already stopped for a red light can load and unload passengers at the same time. For a limited number of childless, young, able bodied passengers, this is true. However, the majority of Americans are neither young nor able bodied, a statement doubly true for many bus riders. They are often old, infirm, disabled, or towing children. Further, during peak periods, the time required to board a number of passengers exceeds the length of the 'red' portion of the traffic signal (<30 seconds). Trying to synchronize the length of a load/unload cycle for a bus with the stop/go cycle is bound for failure.

Any stopped bus blocks right-turning cars, either trying to turn off the road, or trying to turn onto the road. For automobiles, the location of bus-stops is moot. But for buses, far-side stops mean that 50% of the time, a bus will be able to travel through on a green light, rather than having to stop at every light, as if it were red, in order to pick up passengers. Given that signalized intersections represent the majority of delay time for urban travel, this represents a significant savings of time and an increase in travel speed. 

A naive student once lauded the virtues of bus bulbouts as an attribute of an effective transit system. Nothing is further from the truth. Bus bulbouts are the are an attribute of an auto-dominated transportation system. A bus without a dedicated lane travels at about 10 mph (including stops). The more frequently a bus must stop, the slower it travels. Urban traffic travels at about 17 mph. This leads to a demand for 'bus pullouts', where a bus leaves the travel lane. Exiting and re-entering the travel lane takes time, making buses even slower. Solutions include reducing the number of stops and improving bus stops. The latter is worthwhile if there is more than one stop within a 400m distance. (Bus poles are cheap and often too frequently placed).The latter improves bus 'dwell' time at a given stop, typically by improving curb and gutter infrastructure to permit level boarding with minimal gap between curb and bus. (One real advantage of rail over bus is faster boarding, due to more efficient 'docking'). 

Monday, February 10, 2014

Transit System Planning

To effectively model Transit Demand, a simulation program capable of using both a gravity model and a network model is required. Effectively, a Travel Demand Model simulator such as CUBE. Use a familiar model, but make it possible for agencies to "Be the DoT, not the BPR". (Department of Transportation, not Bureau of Public Roads). Map each type of transit to a functional class of road. Treat Light Rail as a highway, regional buses as arterials, flex routes as local streets. Connect centroids only to places within walk distance. Weight propensity to walk inversely to distance. Include a coefficient for quality of the built environment. Treat the first two as 'limited access' facilities, where board is only possible at stops. Lacking Cube, however, it should be possible using ESRI Network Analyst.

Friday, February 7, 2014

On Free Transit

Talinn, Estonia, has free public transit. 

Two things of note:
a) "passenger demand of just 3 percent — and attributed most of that gain to other factors, such as service improvements and new priority lanes for buses"
b) "if any modal shift is happening, it’s that some people are walking less and riding transit more"
The former suggests that service quality and speed matter more than fares. The latter suggests that they are spacing their bus stops too closely (400m), so that the buses are acting a pedestrian circulator, rather than a pedestrian extender. The latter is the more important point.
For buses, there is increasing marginal cost (of delay) per passenger. Every stop makes the journey longer. The more people on the bus, the greater the cumulative delay. If boarding takes 15 seconds, and there are four passengers on the bus, the result is 60 seconds of person-delay. If there are 8 people, the resulting delay is twice as large.
For a pedestrian facing the choice whether to walk or wait for the bus, the per passenger delay caused by boarding is immaterial. The only time-cost is waiting for the bus. If a bus comes every 5 minutes, it is worth waiting about 3 minutes to catch the bus. A comfortable walking pace is 5 m/s, so for any distance over 180m**, it is worth wait to catch a bus. On which basis, bus stops would be placed every 180m. So every four blocks would add a minute of travel time***, per passenger. Ergo, as headway (buses/hour) rises, distance between stops should rise as well.
* 3 minutes x 60 seconds/minute x 5 meters per second
**About 1 SLC block.
***Four blocks-->four stops x 15s delay/stop
'Best Bus', and the 'Bad Bus'. 

Wednesday, February 5, 2014

Reflections on Metropolitan Form and Binary Cities

Accessibility is not purely a field effect, but also a network effect. Rather than the center broadcasting a field effect, the network broadcasts a field of effect, with the strength of that field proportional to the network time-distance to the center. 
Take Binary Metropoli such as Dallas-Ft. Worth or Minneapolis-St. Paul, where two existing monocentric cities have become conjoined. The patterns of sub-centers is distinct from emergent polycentric, where monocentric cities have developed sub-centers. In monocentric cities with radial transit routes, sub-centers emerge as  function of distance from the center. As sub-centers develop sufficiently that their level of activity density warrants it, orbital routes between peripheral sub-centers will develop. For binary metropoli, the pattern is different. The intersection of radial branches between the city centers should emerge as a sub-center.

How does a sub-center differ from an 'Edge City'? Sub-centers have to do with the efficient allocation of retail and services minimize the overlap in market areas, and minimize transportation travel time to the centers.

To use the 'hierarchy of retail' as an example:

  • Regional malls...down to neighborhood,
  • Community Center/Power Center -- big box anchored, 100,000 SF 
  • Neighborhood, 55-60k SF..
  • Grocery anchored
  •  Specialty/In-line (Strip malls)
  • C-Store
The distribution is inversely proportional to their frequency. 

Edge Cities, in contrast, contain more than retail. Garreau characterized them in terms of office development. High-rise office development was traditionally the purview of downtowns, and its emergence outside them was kind of scandalous. High rise office development is associated with higher order services--not personal services and retail, but what is often called "Producer Services", or "Professional Services", characterized by FIRE industries (Finance, Industry, Real Estate).

Tuesday, February 4, 2014

Walking Along the Transit line

Spent a bit thinking about the special case we started with*--walking ALONG the transit line. Basically comes down to two cases: 
1) Get off at Station X, walk to destination.
2) Get off at Station X+1, walk back to destination

For Case 1
--If destination is less than halfway between Station X and Station X+1, walk back.
--If destination is MORE than halfway between Station X & Station X+1, walk to station X+1
Case 2 is much more interesting, and has to do with the walk ratio between the two. 
Getting off at station X+1 means you have to walk to the destination, and then walk back to Station X+1.

Now, for the transit option (Case 2) to be useful, it must be quicker than the transit option (all else equal).
The time to reach a destination using transit is*:
t=d/T + 2x/W

where t = time, d= distance, T = transit travel speed, x = distance of destination from Station X+1, and W is walk speed.
It's 2x, because leaving Station X+1, you still have to walk back to x+1.

Case 1 is always just d/W.
So an area is more accessible to Case 2 than Case 1 when d/T + 2x/W<d/W
If transit is 2x as fast as walking, so that T=2W... (2W, 3W, 4W,6W) we get:

d/2W + 2x/W<d/W
d/3W + 2x/W<d/W
d/4W + 2x/W<d/W
d/6W + 2x/W<d/W
Now I'll assume that the distance between Station X and Station X+1 is 12, and W =1 (making the math simply)
12/2*1 + 2x/1<12/1 --- >   6+ 2x < 12 --- >   x <3
12/3*1 + 2x/1<12/1 --- >   4+ 2x < 12 --- >   x <4
12/4*1 + 2x/1<12/1 --- >   3+ 2x < 12 --- >   x <4.5
12/6*1 + 2x/1<12/1 --- >   2+ 2x < 12 --- >   x <5

Effectively, there is a little 'bubble' around Station X+1 that it is faster to use transit to access, and that bubble gets bigger in proportion to the ratio between the two. However, that bubble does not grow in proportion to the increase in speed. 

      3             2*W
      4             3*W
      5             6*W

Rare is the urban transit that is 6 times the speed of walking. My intuition tells me that most urban rail* is about 3 times the speed of walking, on city street. For any location less than half way, it is always faster to walk. For any location less than 2/3, it is almost certainly faster to walk.

To some extent, this explains the value of streetcars as economic development tools. As 'slow' transit (2.x walking speed), the 'bubble' at the end is very small, so it's very rational to get off and walk the full distance between stops, so that all locations along the corridor benefit from the pass-by pedestrian traffic. If economic development is the sole aim of streetcars, going slower (so long as they are faster than walking) doesn't actually hurt. But getting people to ride streetcars in the first place requires them to provide transportation benefit to a degree where waiting for the streetcar and riding the streetcar is faster than walking.
For longer distances (of light rail magnitude), let me double the distance. I'll assume that the distance between Station X and Station X+1 is 24**

24/2*1 + 2x/1<24/1 --- >   6+ 2x < 24 --- >   x < 9
24/3*1 + 2x/1<24/1 --- >   4+ 2x < 24 --- >   x < 10
24/4*1 + 2x/1<24/1 --- >   3+ 2x < 24 --- >   x < 10.5
24/6*1 + 2x/1<24/1 --- >   2+ 2x < 24 --- >   x < 11
Bigger distances, bigger transit accessible 'bubble' at Station X+1, (all else equal). Makes less sense to make the full walk. This suggests more frequent stops, more economic development, as more pedestrians walk along the transit corridor. The historic form of retail during the transit-centric streetcar age (thin, deep stores) confirms this. Access to street frontage is what matters. Tempting to make really long stop spacing, but there is a distance decay on how far people are willing to walk. Pretty sure their is a way to compare this to walk-trip distance decay (1/x^2) to determine optimum stop spacing for accessibility.

I am not sure how walking ALONG transit compares to TOD access in terms of overall accessibility provided. We habitually calculate 'area accessible to transit' using PI*r^2. When we actually consider how people travel in an urban environment (along street frontages), travel along*** a transit corridor is where the action is. More unique urban land is exposed to a pedestrian (extracted from their car) walking along a transit corridor, than to a pedestrian walking to a destination in proximity to transit station (as there is no return trip along the corridor). Note I do not say the pedestrian has more accessibility (as per our discussions of accessibility isochrones around stations), as each station imposes a time-cost that reduces the average travel speed on transit, and thus the area accessible from the transit network. 

*Headway doesn't enter into it, as all option include boarding and disembarking once.
**This could probably be turned into a graphic like the attached.
***This suggests that a retail arcade between two stations (even if only along 1 side of the tracks) would do rather well, if placed between two closely spaced stations.

Thursday, January 23, 2014


Doing a bit of reading on Planetizen, on an article talking about sprawl repair. The naivite is a little bemusing. Specifically, the McMansions and drive-thru redevelopment.

Awkwardly, much the low-density street development is not worth saving--cheaper to scrape the site and redevelop then to add a facade of new buildings around it. Likewise, the mansion retrofit is unlikely because doing so would require the cooperation of 8 different property owners--a recipe for failure.

Redevelopment authorities sprung into existence for this single purpose--mitigating the problem of parcel fragmentation through land assembly. (Nevermind that their mis-regulation led them to become engines for cities to speculate in real-estate development).

Parcel fragmentation is a big problem in Detroit. I was talking to Dr. Joanna Ganning, who is an expert in 'Shrinking Cities'. Apparently, for all the Rustbelt cities, it's common for half the city to be a successful metropolis, and the other half of the city to be a run-down ghetto of abandoned buildings, un-maintained streets, poverty and crime. 


Reading an interesting paper on urban form, and the author writes: "City compactness can be measured simply using urban spatial form or morphology: the more concentrated the built-up area, the more compact the city is". Which gets me thinking: How is Compactness different from Density?

Planners have moved away from Density, to some extent, on two fronts. First, the Perils of Average Density, and second that density has no rhetorical value---to harp on density "offers no hope to places that are already built at low densities and unlikely to change". For the built environment is a durable place, and changes slowly. Sometimes very slowly. Roads vanish but rarely, and once the development pattern is 'set', very little can be done to change it. 

But what is 'Compactness"? The word has many distinct meanings, but it fundamentally refers to a measure of area. And therein may lay the rhetorical difference--for density, it's a matter of how much stuff is in a given unit of area. For compactness, it's a matter of what unit of area is needed to contain all the stuff. It's a difference of emphasis--the amount of stuff versus the size of the container. What is 'held constant' in each measure is different. For density, it is the unit of area. For compactness, it is the amount of stuff.

Take two hypothetical cities, with the same population. Pi-town is round, constrained within a circumferential wall. Spiderville stretches out in all directions along major roadways. Yet they have the same land area, and thus the same average density. But their compactness is very different. The length of Spiderville's town boundary is much much longer than the Pi-town boundary. 

For transportation, Compactness is a much more important measure then Density. Compactness is also a measure of the distance between any random pair of points within the city. 

This also brings up the interesting topic of fractal density--a city whose edges are yet more scalloped, more indented, then Spiderville, with little tentacles of development reaching out from the urbanized area. 

Monday, January 20, 2014

Davis Connector

Alternatives are not really that different from one another. Must admit a certain amount of irritation with the numbering system. Temptation is to number alignments, and then sub-set them. Better off is to break the alignment into sections, each with shared points, and name the segments of those shared points.

For example, alignment AAA would share the first and third segments with alignment ABA. If someone proposes an alternate route for the middle segment (or part of the middle segment), it becomes 'C', and the alignment is ACA. And then everyone can play mix and match, until there is general consensus on at least PART of the alignment.

Which it looks like they have. All alignment have from Beck/Victory intersection to...near where I-15 and I-215 merge. North end must be the messy part, given that is where they have de-scoped to a more manageable 'minimal operable segment'.

On the south, they have 3--two a block apart, and one next to the capital. Victory Road alignment isn't going to work unless it's bus. Too many impacts on historic properties. Although it did, historically. In modern times, I think it would be impossible to get a LRT vehicle, and difficult to get a streetcar vehicle.

Corridor 2's South end is ridiculous--too sharp for light rail or streetcar, but connects well to State-street buses. 400w seems simply to connect to TRAX then 300w. The 'loop' on 5a/5b is madness--to much cost/mile for rail. In Bountiful, Alignment 2 is preferred for job access--not sure what the intent of 3a/3b--high density housing? Corridor 6 doesn't get close enough to the high-density residential to make it worthwhile. Corridor 3a/3b are decent, as are 1 & 4. Ideally (for light rail) I'd want the bottom of 4 and the top of 1. Irritatingly, none of the alignments reach South Davis Community Hospital, or Lakeview hospital, both of which are major employment centers.

For mode, the distance (~10 miles) is too far for streetcar. For a 'bare field' city, BRT would beat light rail hands down, but UTA already has the maintenance center and vehicles for LRT, which should make it cheaper per mile than normal. But it's hard to make the call on mode without knowing how much is going to be  exclusive right of way, and where the stations are going to be.  At $30m/mile, and nothing worth stopping for along Beck street, BRT seems like the better option. And thus, alignment 2.

Census' OnTheMap shows a slug of jobs at 500 North and Highway 89 (500w).

Hilariously, someone mentions that they don't want streetcars on their historic Davis County streets....where streetcars used to be.