HSR and Self-driving vehicles

Christian Wolmar writes: Innovation ignored at our peril :

“One of the reasons for my scepticism about HS2 is on the basis that it does not take into account future development of technology. Just look at how technology has changed since 1993 when mobile phones had barely taken root, Google, Facebook and Twitter were but twinkles in their founders’ eye and digital TV was just starting. Will there really be enough people wanting to pile into what are likely to be expensive trains in 20 years time to justify the huge expenditure on this project?
And here’s where I stick my neck out. The next big technology, one with such huge implications that it is impossible to being to predict them, is driverless cars. Google, which is investing billions in the project, announced back in August that its fleet of more than a dozen driverless cars had completed 300,000 miles – ten times round the world – without an accident. The cars have driven through San Francisco and through various parts of California and Nevada – where a law has been passed allowing them – and while there are no plans to produce them commercially yet, their time will inevitably come.
Perhaps they will start by being driven only on motorways but even that would have enormous consequences. It would combine many of the advantages of train travel with the flexibility of car use. Think trucks, too. The economics of transport would change as radically as they did when the railways were first developed. The time frame may be a decade or two, but the consequences will be much more far reaching than, say, the much talked about electric cars. The driverless car – or rather motor vehicle – is the innovation that we ought all to be taking into account in our future thinking.”

It’s Toasted

Global Warming needs an advertising campaign. While those trying to stop it are well-funded, and many organizations try to deny it or minimize its effects, almost no one is selling us on its merits. Global warming opponents make is seem like the earth is going to become a dried up desert-like husk. One of my friends insists it’s too late, the Earth is Toast.
Embrace that idea. Instead of the “Earth is toast”, we need to say It’s Toasted, giving the new and improved earth a warm and cozy feel, like a hot breakfast on a Winter’s Day. And every day, we are slightly more and more toasted.

Just-in-time consumption: Does the `pint of milk test’ hold water?

Cross-posted from streets.mn: Just-in-time consumption: Does the `pint of milk test’ hold water?

“As with stores, houses too are getting larger over the long run. New suburban homes have more space to store goods in-house. While urban residents export storage to common stores, suburban residents more likely to have second freezers, have more space to store stuff.”

Just-in-time consumption: Does the `pint of milk test’ hold water?

Just-in-time production revolutionized manufacturing, enabling both a reduction in inventories as supplies arrive only shortly before needed, and an improvement in quality as poorly made inputs are no longer stored for long periods of time, but can be quickly identified and feedback provided to the supplier. The widespread adoption of the just-in-time process is itself the product of the logistics revolution, information and communications technologies, containerization in shipping, and the modern freeway system. It has seen a concomitant change in the retail sector, which has brought about fewer and larger stores at a greater distance from the end consumer.The notion of “just-in-time consumption”, (acquisition of a good by the end consumer shortly before its use, rather than being acquired and stored for future use) though seemingly a natural mirror to the more widely used “just-in-time production” has not received the same attention. The phrase itself, only generates 212K hits in Google, (significantly higher than 2007, and of which the original version of this post rates #2) of which only a few are on-point, in comparison to over 2.23M for “just-in-time production”.Yet many goods and services are already consumed in a just-in-time manner. Most notable is energy, which is delivered on-demand to users, who no longer store coal at home for the furnace, but instead buy natural gas or electricity as needed. (The slowly vanishing home heating oil remains an exception). Other services that are provided on-demand or just-in-time include water and sewer, communications (internet, telephony, and television). What is in common about these disparate technologies is their network nature, the large infrastructure required to enable using the flows on-demand. While sewer is a continuous service for most people (those who do not have septic tanks), garbage is typically only collected periodically (e.g. once a week), and recycling less so (e.g. fortnightly).Other goods once saw regular to-the-house delivery, especially in suburban areas. Foxell [2005] writes of goods and services found in Metro-land, the idyllic north London suburbs built by the Metropolitan railway in the early twentieth century:

“This service economy is illustrated by the variety of tradesmen that called at our home: the milkman twice a day, with a horse-drawn cart; the baker once a day, with a large upright barrow on two wheels, the handles of which lifted him off the ground when going down hill; the postman thrice; the butcher’s boy by bicycle twice a week; and the grocer twice a week. Others like the coalman or the Gas, Light & Coke Co. in their steam-powered Sentinel lorry also made regular deliveries. Over a longer period, visits could be expected from the men from the Prudential [insurance], Hoover [vacuum cleaners], Singer [sewing machines] and the like – all using a service call to take the opportunity to sell new products. There was something reassuring about seeing such familiar faces and catching up with the latest gossip. In addition there were the itinerant callers such as Walls Ice Cream man on his tricycle as well as the French onion sellers, gypsies with pegs and posies, rag and bone men, tinkers [metalsmiths] and the knife-sharpeners with their pedal-driving grinding wheels.”

Today, the vast majority of those goods are not acquired at home but in stores or online. Delivery services have replaced salesmen, as the two functions (delivery and sales) are now distinct and specialized. Today’s visitors might be the post office, FedEx or UPS, and the pizza delivery boy.

Just-in-time does not require delivery to the residence, it can involve ubiquity in the placement of stores, so that they are near the end consumer. Traditionally the retail store was just that, a place where a community could store goods, and individuals could take or buy them as needed. A new model of temporary lockers may emerge to fill the gap.


Many planners would like to make the ability to acquire goods just-in-time without the use of a vehicle a normative planning standard. For instance, a report, Beyond 2010: A Holistic Approach to Road Safety in Great Britain calls for the “pint of milk test”, for all new developments, whereby a resident can get to a shop to buy a pint of milk in 10 minutes or less without getting in their car [Parliamentary Advisory Council on Transport Safety, 2007]. The idea of 10 minutes comes from people’s willingness to walk, people are less willing to walk longer distances than shorter, and 10 minutes (or one-half mile (0.8 km)) seems to be a threshold over which walking tolerance seems to drop. This distance was derived from several empirical studies, including Pushkarev and Zupan [n.d.], who showed the median walk by travelers accessing the New York subway was 0.35 mi (0.57 km), while the median walk to access commuter rail stations in suburban New Jersey was 0.5 to 0.6 mi (0.8 – 1.0 km). Results from the 1983/84 National Personal Transportation Survey reported by Unterman [1990] found shorter distances: 70 percent of Americans will walk 500 feet (0.15 km) for normal daily trips, 40 percent walk 1,000 feet (0.31 km), and only 10 percent walk a half-mile (0.8 km).The pint of milk refers to a standard quantity of a highly perishable and frequently consumed good. The objective of avoiding car use is obvious for a group advocating road safety. The pint of milk test has received some currency in England, being noted by several studies in recent years [Bennett and Morris, 2006, Marsh, 2004]. This is a particular issue in a crowded city like London, where auto ownership is lower than suburban areas, roads are more crowded, and parking more difficult even for those with a car.

The trends in retailing have been clear in the United States for a long time. Stores are over the long term getting larger and gaining larger market areas [Yim, 1990]. Small stores serving local areas have been losing market share to larger stores which bring with them economies of scale. Efforts to reverse this trend have met with resistance from retailers, consumers, and neighbors [Nelson and Niles, 1999].

Illustrating this trend, the Food Marketing Institute reports in 2011 there were 36,569 supermarkets (with $2 million in sales or more, noting the median annual sales for a supermarket was $17 million, and average size was 46,000 sq. ft. (slightly down form a 2005 peak of 48,058, indicating an increasing number of smaller markets in recent years, but nowhere near retracing the long march upward). The average number of trips per week consumers make to the supermarket was up to 2.2. (from 1.9 in 2006).

In 1930, The Great Atlantic and Pacific Tea Company, at the time the leading US supermarket, alone had 16,000 stores with a combined revenue of $1 billion (or per store revenue of $62,500 in 1930 dollars, estimated to be $754,000 today) [The Rise and Decline of the Great Atlantic and Pacific Tea company, n.d.]

Handy [1993] claims “the automobile instigated a collapse of the retail hierarchy by encouraging the growth of community and regional centers at the expense of local shops and the central business district. The result has been a cycle of dependence, in which suburban communities are designed for the automobile leaving residents little choice but to drive.”

As with stores, houses too are getting larger over the long run. New suburban homes have more space to store goods in-house. While urban residents export storage to common stores, suburban residents more likely to have second freezers, have more space to store stuff.

While the number of freezers per household in the United States is declining as second freezers are being retired and not replaced, the number of refrigerators is increasing slightly, due to households obtaining second refrigerators. [Wenzel et al., 1997]. While no immediate inference can be made about this, other trends are also at work. Total refrigerated and frozen space has not been computed, though the average size of a house’s primary refrigerator or freezer is likely increasing. Food may last longer in refrigerators than it used to due to the addition of preservatives (though the trend of increased consumption of organic foods may reverse this). Further globalization may mean that fewer goods are seasonal and need to be accumulated prior to their being out-of-season.

Persson and Bratt [2001] note that e-shopping may induce the installation of a second set of fridge/freezers per household to receive delivered goods. This additional electricity consumption has environmental consequences; already, there are 2.2 refrigerators and freezers per household in New Zealand (Roke, 2006) cited in [New Zealand Ministry for the Environment, n.d.].

If urban residents do undertake more just-in-time consumption than suburbanites both because of the higher storage costs associated with smaller houses, and the greater opportunity afforded by more stores nearby, we would expect to see this show up in the travel behavior data that is collected by urban regions.

variable Minneapolis St. Paul Remainder of Hennepin County
Year Structure Built 1926 1929 1970
Sq. Ft. 1773 1826 2152
Sq. Ft. per Person 822 755 810
Households with No Cars 5900 2800 2500

Table 1 illustrates some of the differences between the City of Minneapolis, suburban Hennepin County (Hennepin excluding the City of Minneapolis), and the City of St. Paul in neighboring Ramsey County. Residents of Minneapolis live in older houses (average year built of 1926 vs. 1970 in the suburbs) with 1773 square feet vs. 2152 in the suburbs. However because of the lower household size, city residents actually have slightly more area per person. Further Minneapolis residents are more likely to be carless.

According to the 2000/2001 Twin Cities Travel Behavior Inventory among residents of the City of Minneapolis, 12.8 percent of daily trips were for shopping 5 while for Hennepin County excluding the City of Minneapolis the number was 12.2 percent. Thus Minneapolitans devote 5 percent more of their trips to shopping than suburban Hennepin County residents.

Minneapolitans also make slightly more trips than their suburban brethren, 3.81 per day vs. 3.70 for suburban Hennepin. (The unpublished 2011 TBI will likely show significantly lower numbers here). Given the small differences and their temporal instability, it probably is unreasonable to make much of them.

The evidence supports the hypothesis that city residents who have somewhat higher accessibility (see Figure) to neighborhood stores and somewhat reduced storage space at home shop more frequently.


Broadly, there are two types of places, those that satisfy the pint of milk test, and those that don’t. Similarly, there are two kinds of people, those who care about the pint of milk test and those who don’t. The problem comes from the mismatch of those who care but live in places that are unsatisfactory. (Those who don’t care but live in places passing the test are probably okay). If self-selection is at work, these cells are not randomly distributed, but people who want to live in particular environments do so. People who prefer milk-accessible areas bid up prices in those areas, while those who are indifferent (or perhaps lactose-intolerant) move out. However, if preferences change faster than spatial structure, there may be a mismatch.

Policy that excludes mixture of residential and commercial development may also foster a mismatch.

Evidence from the Twin Cities bears on the issue (Figures 2 to 5). According to the American Housing Survey [US Census Bureau, n.d.], over 80 percent of residents in the City of Minneapolis report satisfactory neighborhood shopping within a mile of home, compared with 70 percent of those in suburban Hennepin County (Figure 2). Despite that positive assessment of shopping, suburban Hennepin residents have a better opinion of their own neighborhood than those in the City of Minneapolis (Figure 3). The problems these urbanites report in greater numbers than their suburban counterparts are noise and traffic, crime, and odors (Figure 4).





When people move, they are doing so to places they believe are better, but for all residents it is the home that is better than previous much more so than the neighborhood, and in Minneapolis, only a third rate their current neighborhood as better than their previous (in contrast to half of suburban residents) (Figure 5).

To the extent neighborhood shopping enabling just-in-time consumption of the pint of milk is important to people, cities fare better than their suburbs, but if the cost of that neighborhood shopping is other urban ills, people will make the trade-off, sacrificing access to retail to have access to quiet and congestion free, safe, and pleasantly smelling suburban environments.

Whether this is a social good is another question entirely, and depends on relative efficiency of urban goods delivery services, energy efficiency of in-store displays vs. at-home refrigeration units, and numerous other questions.


  • Bennett, J. Morris, J. 2006 , Gateway people, Technical report, Institute for Public Policy Research.
  • Foxell, C. 2005 , Rails to Metro-Land., Clive Foxell, Chesham, Bucks, England.
  • Handy, S. 1993 , “A Cycle of Dependence: Automobiles, Accessibility, and the Evolution of the Transportation and Retail Hierarchies”, Berkeley Planning Journal , Vol. 8, pp. 21-43.
  • Heiskanen, E. Jalas, M. 2000 , Dematerialization Through Services: A Review and Evaluation of the Debate, Ministry of Environment: Edita, jakaja.
  • Herman, R., Ardekani, S. Ausubel, J. 1990 , “Dematerialization”, Technological Forecasting and Social Change , Vol. 38(3), pp. 333-347.
  • Marsh, G. 2004 , “Tesco piles ‘em high: Flats above supermarkets are a good buy”, The Times , Vol. June 18, 2004.
  • Nelson, D. Niles, J. 1999 , “Market Dynamics and Nonwork Travel Patterns; Obstacles to Transit-Oriented Development?”, Transportation Research Record , Vol. 1669, Transportation Research Board of the National Academies, pp. 13-21.
  • New Zealand Ministry for the Environment n.d. , Technical report.
  • Parliamentary Advisory Council on Transport Safety 2007 , Beyond 2010: A Holistic Approach to Road Safety in Great Britain, Technical report, Parliamentary Advisory Council on Transport Safety. Parliamentary Advisory Council for Transport Safety http://news.bbc.co.uk/1/hi/uk/7046200.stm.
  • Persson, A. Bratt, M. 2001 , “Future CO 2 savings from on-line shopping jeopardised by bad planning”, Proceedings of the 2001 ECEEE Summer Study ÔFurther than Ever from Kyoto .
  • Pushkarev, B. Zupan, J. n.d. , “Where Transit Works: Urban Densities for Public Transportation”, Urban Transportation: Perspectives and Prospects , pp. 341-344.
  • The Rise and Decline of the Great Atlantic and Pacific Tea company n.d.
  • Unterman, D. 1990 , `Accommodating the Pedestrian: Adapting Towns and Neighborhoods for Walking and Bicycling. Personal Travel in the US, Vol. II: A Report of the Findings from 1983-1984 NPTS, Source Control Programs’.
  • US Census Bureau n.d. , American Housing Survey for the Minneapolis St. Paul Metropolitan Area, Technical report, US Census Bureau. 1998AHS: Minneapolis h170-98-9.
  • Wenzel, T., Koomey, J., Rosenquist, G., Sanchez, M. Hanford, J. 1997 , “Energy Data Sourcebook for the US Residential Sector”, Lawrence Berkeley National Laboratory, Report , Vol. 40297.
  • Wernick, I., Herman, R., Govind, S. Ausubel, J. 1996 , “Materialization and Dematerialization: Measures and Trends.”, Daedalus , Vol. 125(3), American Academy of Arts and Sciences.
  • Yim, Y. 1990 , The Relationship Between Transportation Services and Urban Activities: The Food Retail Distribution Case, PhD thesis, University of California, Institute of Transportation Studies.

Adapted and updated from a post on The Transportationist Nov. 8 2007.

StarTrib on Gender and Driving, and the Oh-so-timely Death of “Woman Driver” Jokes – Network Distance

Jessica Schoner @ Network Distance on: StarTrib on Gender and Driving, and the Oh-so-timely Death of “Woman Driver” Jokes

She writes

“Given all these external forces that influence travel needs and choices, my conclusion is that there is likely no inherent physiological difference causing the difference in travel behavior; or if a biological difference exists, it is marginal and unmeasurable relative to these larger forces. These social, economic, and cultural forces shape the stereotypes of male and female drivers that we are so familiar with.”

I agree culture is important. I disagree that physiological differences don’t have effects. In particular, I think culture has a large biological component (culture and biology are mutually co-evolving systems). Risk taking has clear biological elements to it, and obviously drives a lot of traffic safety issues.

Fastest Metropolitan Area in the United States (outside of California) | streets.mn

Cross-posted from streets.mn: Fastest Metropolitan Area in the United States (outside of California)


Fastest Metropolitan Area in the United States (outside of California)

Minneapolis mn

If I told you that the Minneapolis-St. Paul- Bloomington Metropolitan area had the highest average speeds (outside of California) of the fifty largest metropolitan areas in the United States, would you be surprised? I was. According to data released with the 2012 Texas A&M’s Transportation Institutes’s Urban Mobility Report, Powered by Inrix,Table A-8 reveals year 2010 speeds on freeways and arterial streets. Our freeway speeds are slightly below average (54.3 MPH). Our arterial speeds are as fast or faster than anyone else’s (39.6 MPH), and a VMT-weighted average of these two numbers (I estimated 45 MPH) results in higher peak speeds than you find in any other of the fifty largest metropolitan areas (which average 38.1 MPH) outside of California.

What is an arterial? “An arterial road is a moderate or high-capacity road which is immediately below a highway level of service.” A principal arterial is generally on the National Highway System. Minnesota’s guidelines are here. The Metropolitan Council’s study is here (and includes freeways as part of the principal arterial system). It is not exactly clear what definition Inrix used, but since the table says “arterial streets”, I will take it to be anything not a freeway on which they had sufficient sample size to estimate a speed.

The Metropolitan Council’s full classification map is quite large, and here. Anything in red is a principal arterial, other arterials are also identified.

Anyway, who cares about congestion if the road is fast. We can go five miles farther per hour than people in the average city, and thus reach more destinations, and be more productive with our time.

(Yes, this is probably not good for pedestrians).


With more total driver’s licenses, women passing men on the roads

Aimee Blanchette @ Strib: With more total driver’s licenses, women passing men on the roads :

The jokes about dreadful female drivers can officially take a back seat.
For the first time ever, more women than men have driver’s licenses nationwide. This gender gap reversal means safer roads and less pollution.
That’s according to the University of Michigan’s Transportation Research Institute, which says that in 2010, 105 million women held licenses, compared with 104 million men. Women are more likely to purchase “smaller, safer and more fuel-efficient vehicles” and “drive less and tend to have a lower fatality rate per distance driven,” said Michael Sivak, the study’s co-author.
The stereotype, however, has been a joke as long as women have been driving.
“It wasn’t true and I don’t think people find it funny anymore,” said David Levinson, a professor in the Department of Civil Engineering at the University of Minnesota.“Statistics have long shown that the average woman is a slightly safer driver than the average man.”

Accessibility Now and in the Future


The Webcast for Accessibility Now and in the Future is now available. (Andrew Owen presented it at CTS yesterday). The presentation is also available for download.
The full research reports are:

Sidewalks are Hotting Up

Brendon writes in:

Heating a sidewalk section has climate change implications. I calculate the 26-year cost of your section at $8,722 at the low end and $9,708 at the high end (depending on the discount rate you assign to the future impacts of climate change. I tend to lean towards the higher end). This means your break-even point is 8% to 20% higher, meaning maybe 173 to 192 pedestrians per day. Of course with a carbon tax in place, there would likely be more walkers in some places, meaning heating the sidewalks become feasible in more places.
Now, if you could use waste heat that hasn’t been previously captured to heat sidewalks, as they are proposing to do with the new “interchange” plaza and HERC steam, the carbon footprint becomes effectively zero additional. Much less per kWh/BTU.
Other interesting facts, heating all the sidewalks in Minneapolis with electricity from the grid for one year would produce more greenhouse gases than the disposal of all our solid waste and wastewater does over the same time period. The additional energy consumption would be equal to about 1/3 of the current annual consumption in all residential properties in the city. It would increase the city’s annual electricity consumption by 8%.

He nicely identifies a feedback effect, heating up sidewalks will create more emissions, which will heat the atmosphere, which will eventually negate the need for heating up sidewalks. There must be an equilibrium point here.
More seriously, the use of waste heat is a great idea, especially near the HERC. The problem would be building infrastructure to distribute that more broadly. There might also be waste heat from wastewater (which is still liquid in the winter, and thus warmer than the ground around it) which we don’t capture, or let go to roads, by running sewers under the streets rather than the sidewalks.

Walkable Ice

In the absence of significant global warming, Minnesotans still need to contend with ice on the sidewalks (to be clear, in the presence of significant global warming, we would have other problems; and in the presence of significant global cooling, we would face snow and glaciers rather than freezing rain and ice).
My own house suffers this problem, despite (or because of) snow clearance, ice re-forms on the sidewalks and steps, or freezing rain falls on the cleared sidewalks, making them slick, rather than on snow-covered sidewalks, making them crunchy. Further, water drips from the house and gutters because of ice dams, and then freezes on the ground.
My alma mater, Georgia Tech, while not typically subject to much snow or ice, has many sidewalks just above steam-heat pipes, which would clear those sidewalks pretty readily in most conditions. The University of Minnesota does a pretty good job with snow clearance, all things considered, using a lot of labor and snow clearance machines in the process.
Ice clearance is hard in this freeze-melt cycle, especially when the water has no where to drain because (1) the sidewalks are convex (along either width or length), (2) the boulevards are covered in snow creating no place for run off to go and creating a source for new melted water, (3) the storm drains are covered in snow, and (4) the ground is still frozen and/or the soil above the freeze line is super-saturated.
I see a lot of attention to ice-free roads, and very little for ice-free sidewalks. This would greatly enhance walkability, reduce the likelihood of severe injury, and increase the number of pedestrians.
There are a variety of ways to address icy sidewalks:

  • Mechanical: clearing sidewalks with shovels and pick-axes and snow-bots.
  • Friction: Sand, Grit, Gravel make the ice more walkable (by increasing friction);
  • Chemical: Salt (reduces ice via melting);
  • Radiant: heated sidewalks (using a variety of techniques);
  • Protection: covered sidewalks; and

If we consider the cost of an icy sidewalk equal to the probability of a fall multiplied by the cost of a fall, multiplied by the number of people who face that probability per day, times the number of days the sidewalk is icy, we can get a sense of the amount we should invest to avoid the ice.
Let’s say I fall once a year on the ice (typical), after traveling 2.6 km * 2 times a day * 10 ice days = 52 km. My fall rate: is 1 fall per 52 km of ice.
For a house with 10 m of frontage, with 100 pedestrians a day, it gets 1 km of pedestrian traffic per day. Once every 52 icy days, it will see someone fall.
The cost of a fall is unclear, since most falls are unreported. For reported falls which require medical care, the estimate is on the order of $10,000. Let’s assume 10% of falls require medical attention, meaning the average cost per fall is $1,000.
This implies that every 52 icy days (once every 5.2 years if there are 10 icy days per year), each house with icy sidewalks imposes $1,000 in costs. In that case, if we want to minimize social costs, we should be willing to invest $19 day in effective ice clearance. This is about an hour of labor (or two hours of undergraduate labor) to operate simple machines plus some cheap (Friction or Chemical based) treatments). Unfortunately, I am unclear whether $19/day is effective.
We could add delay costs, due to people walking slower on ice, which I estimate to be about a 10% reduction in walking speed. With a travel speed typically of 1.44 m/s, we might decrease that to 1.3 m/s. So instead of the 100 pedestrians taking 7 seconds each to walk in front of the house, they are taking 7.7 seconds. That is 70 person-seconds per day, which has an economic value of (@ $15/hour) of $0.30 per day, two orders of magnitude lower than the fall costs, and so not really worth discussing further.


But can we prevent the ice from forming?
For $1000 every 5.2 years, we get $5000 for a 26 year expected life of a capital investment. If we can make a capital investment of less than $5000 to eliminate falls on our public sidewalk, it would be socially worthwhile.
The cost of heating sidewalks is about $20 per square foot (or about $215 per square meter). A 10 meter by 2 meter sidewalk is 20 meters square, giving us a cost of $4305.
We must consider operating costs, which are estimated at $.60/hour. If it is operating 240 hours per year (this is a guess, I don’t know how long it needs to operate to keep the sidewalk ice free), this is $144 year. (You might run it to melt snow, but that has fewer benefits, just avoiding shoveling, not reduced falling in this simple model, so I don’t consider that). $144 per year is $3744 over 26 years (no discounting), so is a large fraction of the capital costs.
Unfortunately, $4305+$3744 > $5000, so 100 pedestrians is not enough to justify heating. However 160 pedestrians would be a break-even point.
Covering the sidewalks (200m of roofing) could cost $80/square foot ($860/square meter). This lasts 15 years. For 20 square meters, this costs $17,200, well out of range for our residential sidewalk if the only objective is ice reduction, especially since it only lasts 15 years. It might have other benefits, such as reducing our exposure to nature and street-life though.
Policy recommendation: Use student labor to clear sidewalks with low pedestrian flows. Heat sidewalks which have high pedestrian flows. Cover sidewalks with very high pedestrian flows.
Yes, I did fall this year. This post was written between my vertical and horizontal positions, so I apologize in advance for its rushed nature.