Curtailing Transportation Generated Greenhouse Gases

Comment on this page here.

The several basic ways that carbon in the passenger transport system can be reduced or eliminated is illustrated in Figure 1 in Appendix.

Use Vehicles More Efficiently

In essence, the right side of the diagram lists the ways of accommodating person travel with fewer miles of motorized vehicle movement. That means shifting person travel to non-motorized modes and increasing the occupancies of motor vehicles. Increasing the average vehicle occupancy is accomplished either by giving people better ways to fill up vehicles, or by raising the price of motor vehicle travel faced by the traveler.

Raise the price of travel

If the price of a vehicle mile is raised, people will have an incentive to share vehicle miles, thus reducing vehicle miles traveled (VMT).  A reasonable price target would be the actual cost of providing travel services and facilities.  A system of transportation that meets this target would be far more efficient in use of energy.  There would be many fewer cars, more transit, and many more trips made on foot and by bicycling. Since the system is so heavily subsidized now, a smooth transition to full cost pricing would likely take years. Nevertheless, the target is consistent with minimum GHG production.

Match vehicle types to passenger trips

Except for motorcycles and bicycles, most passenger vehicles are oversized for the number of passengers they usually carry, and therefore require more fuel than if they were perfectly sized.  To some degree, this excess seating capacity is a practical necessity.  For example, when a buyer purchases a car, the size of the car is generally related to the largest number of people the buyer expects to carry, even though the normal number is one.  Bus size may be determined by the largest number of people expected to be on board over the course of a route during the busiest time of day, as well as by standee policies.  There are ways to improve the efficiency of utilization.

Effect of population density

The key enabling factor for the three carbon reduction approaches on the right side of Figure 1 is density of land use. High density, mixed-use development lets people meet most of their needs near their homes, so they can walk or ride bikes. Higher transit density makes their longer trips more convenient. Car travel is slightly less convenient

In the early 1990s, John Holtzclaw used actual mileage records of vehicles owned by residents of high and low density areas in the San Francisco Bay area to determine the relation between VMT and urban density. He found a consistent relationship, that per capita VMT is reduced 30% by a doubling of population density.

In 2000 he presented another paper in which he included other variables and other cities. After accounting for residential density, transit density was the most important variable in reducing VMT. 

How population density can be increased

Most of the great high-density places in the world evolved before the car was available. How can cities developed during the automobile era be densified?  Presuming that uniformly densified sprawl would be neither practical nor desirable, we have to think in terms of dense nodes of development.  For that the essential catalyst is rail transit.  It is the only practical way of bringing about a nodal density pattern, due to its capability of carrying large numbers of people efficiently between widely separated stations, and because of its deserved reputation for permanence. Permanence (i.e., commitment to long term service) is what gives development interests confidence to make long-term investments.

With suitable attention and municipal vigor in developing around the stations, a lot of people can have the benefits of walkable communities. With the stations in the centers of cities, the development will be drawn inward, away from the UGBs, to help in preserving rural Sonoma County.

Although the overall density of the County will remain low, the density at which most people actually live can grow significantly, even though most of the housing stock in the County today would remain pretty much as is.  The choice of living in low-density surroundings will still be available to people that prefer it, but it will be subject to market conditions.  We can't expect people who live in high-density areas to continue subsidizing the folks who prefer something else.

Housing at rail stations

Rail ridership is higher when rail station areas are predominantly housing rather than workplaces or commercial. People who live there can get by with fewer cars because they can meet many of their needs on foot or bicycle, and the bus service there is better. For any of their longer trips that could be made on rail transit, the station area residents have a strong tendency to take the train.

When workplaces dominate the station area, many of the workers are from suburban areas. They depend on cars at home, and therefore have a tendency to drive to work, even if it is near a rail station.

Correcting transportation finance structures

In large measure, our excessive dependence on automobiles derived from methods of financing the infrastructure that separated the paying from the using. That being so, freeing ourselves from that dependence will entail backing away from that separation by linking use to payment. Although many of these problems are brought about by laws and practices at state and federal levels, here are some that are under local control:

• Unbundle the cost of parking from commercial and residential leases and rentals.
• Reduce requirements for on site parking for commercial and residential development.  Permit conversion of current parking spaces to higher uses.
• Levy tax per parking space, coupled with permission to land owners to pass costs through to drivers.
• Allow neighborhoods, both residential and commercial, to rent out parking spaces at their curbside.
• Charge market rates for parking, even for access to transit.
• Segregate transportation related expenses within municipal budgets and offset them with taxes or fees paid by transportation users.
• Levy land taxes on the land underlying roadways, with the taxes paid by road user fees.
• Institute a county fuel tax increment.
• Change the way motorists pay for their travel: shift annual payments into payments “by the mile” or “by the hour” wherever practical.

Personally Choose Fuel Efficient Transport

In Sonoma County our transportation sector is emitting the greatest amount of CO₂ pollution of any sector (42% of total).  This growth has exceeded the national average (up 43% from 1990). Working towards a net zero carbon will require a series of important and drastic changes in the way we move.

 Personally choosing a carbon efficient transportation mode is probably the single most important choice we can make right now. As shown in Table 1, there are large differences in efficiency between various transportation modes.

Table 1

The figures in Table 1 are all national figures calculated by the actual use of fuel by each sector. Care must be taken to note the persons per vehicle (load factor) used in the calculation to see where the most improvement can be made.  For example doubling the riders in an AMTRAK car or bus will halve the energy consumption of the system whereas the van pool and airplane seem nearly filled.

 Nevertheless, the above figures are not the best we can do.  Many available choices do much better than these national averages.

•  The Toyota Prius uses 2250 BTU/ Passenger Mile with the standard load factor of 1.57. Carrying four people it's ____BTU/passenger mile.
• Toyotas RAV4 Electric uses only 1,024  BTU with a loading of only one passenger uses ____BTU/passenger mile. With four people it's only ____BTU/passenger mile.
• The two seater, high performance, the tzero (AC Propulsion) uses only 682 BTU.  That's just 341 BTU/passenger mile with a passenger. It will also go 0-60mph in 6.2 seconds and travel over 300 miles at highway speeds.
• An electric bike or scooter running on 200 watts will use only 45 BTU or about one-one hundredth of a personal truck with just the driver. 

The published mileage ratings posted on new vehicles are helpful in choosing a low polluting, efficient vehicle, but serve only as a relative guide.  These ratings are the result of tests done by the EPA on new, perfectly conditioned cars and trucks. Your mileage may vary. The Highway Driving Cycle test lasts 765 seconds, travels a distance of 10.2 miles, and reaches a maximum speed of 59.9 mph.  The average speed is only 48.2 mph.(Table 4.3)  Real world highway driving will yield much poorer results.  In EPAs own testing vehicles had as much as a 30% drop in fuel economy as the speed was increased from 55mph to 75mph (Table 4.25).   Across all vehicles, expect a drop of 17% as the speed increases from 55mph to 70mph. This fact makes a case for lower speed limits as regulated during the last fuel crisis. Still the EPA ratings are a good relative guide.  Checking the mileage when the tank is filled is the real way to know what you're getting.

Nationally 52% of all light vehicles sold are not even cars.  They're SUV s, light trucks, and vans.  In 2003, 27% of all light vehicles sold were SUV s.  The percentage is likely even higher in Sonoma County.  Nationally, the average 4X4 truck was driven more miles than the average sedan or wagon.(Figure 7.2) These vehicles are in a class by themselves outside of the minimum pollution standards of automobiles must follow. Leaving these truck class vehicles at home when not filled and taking a small fuel efficient 3 or 4 cylinder car instead is a big, first step in the right direction.

Make Vehicles More Carbon Efficient

There is a direct correlation between vehicle weight and fuel efficiency.  A 10% weight reduction yields, on an average, an 8% reduction in fuel use.(source) Smaller, lighter, and more aerodynamic vehicles can greatly reduce our fuel consumption.

Diesel engines have a natural fuel economy advantage over gasoline engines.  Their high compression gets more power out of every combustion pulse giving a 20 to 30% advantage. Sub compact turbo diesels sold in Europe can get over 90mpg on highway tests.  (There are some pollution issues other than carbon.)

 Electric drive systems are extremely efficient compared to heat engines. Electrics convert from electrical to mechanical power from about 75 to 90% efficiency.  Compare this to heat engines at 15 to 30%.  This fact gives electric vehicles, hybrids, and fuel cell vehicles their big advantage.

 Use a Renewable Carbon Fuel

Vegetable oils, biodiesel, and alcohol are all renewable liquid fuels that can replace fossil fuels. They are safe to be around and transport easily.  In almost all ways they are a perfect replacement for our transportation fuels. They are the physical precursors of crude oil and a purer form that can burn more completely.

 Vegetable oil can be used in slightly modified, but easily available, diesel engined vehicles. This includes most large trucks and some autos (Mercedes, Toyota, and Volkswagen models).

 Biodiesel can be used in the above vehicles without any modifications.  It can even be mixed in the tank. Both wood and grain (methyl and ethyl) alcohol can be mixed into gasoline to form a blend.  Most of the gasoline we buy is a 10% blend (source?) Motors can be modified to run on 100% alcohol with good results [Brazil (source)]

Every gallon of these three fuels has to be grown, harvested, processed, and transported to a fuel station before we have a chance to burn them. To be carbon neutral this energy has to come from a renewable source. This is not a small problem. The tractors might be solar electric or biodiesel, the factory may run on solar electricity or hydroelectricity, and the transport truck on vegetable oil. However, all this energy needs to be subtracted from the energy released from that gallon of fuel. These liquid vegetable based fuels are an attractive replacement but because of the high energy input required they will ultimately be limited by the land, water, and sunshine needed to grow them.  As a county we should be using as much of this fuel as is available especially on a recycled or scrap basis (used cooking oils, food process oils, alcohol distilled from agricultural waste etc.)

Electricity

Electricity is, of course, widely available. Most intercity rail systems are electrically powered. There are a few battery driven cars and trucks available. Electrics have the advantage of zero tailpipe emissions and quiet operation.  They have a simple and straightforward design. 100-year-old systems such as the New York subway system work perfectly well today. Electric trams are gaining ridership and new tracks.(source)