1. Urban Management Han, Haoying 韩昊英 PhD, Associate Professor
Department of Land Management
College of Public Administration
Zhejiang University
Mobile:
Tel:
for the course —
ID: urbanmanagement, Password: urban.management 1

2. Transportation

3. Keynotes What do transportation planners do? – four basic tasks
The four-step process
Limitation of the four-step process
Transportation system management (TSM) techniques
6 Issues that engage transportation planners
What is congestion tax?
How much should congestion tax be?
What are alternatives to congestion tax?
Slide 3

4. Transit Railway

5. Tourism Railway

6. One-Track Railway

10. Traffic Jam in Hangzhou

13. 1. What do transportation planners do?
Most transportation planners are engaged, to some degree, in four basic tasks:
Estimating future demand for transportation facilities or services;
Proposing and evaluating alternative ways to respond, either by supplying more or different services or by attempting to modify demand;
Calculating the costs of various responses or policies, using many definitions of cost;
Evaluating the options and recommending the solution most appropriate for the situation.

14. 2. The Four-Step Process Estimating trip generation
Land use, socioeconomic data
Estimating trip generation
Estimating trip distribution
Estimating model split/ mode choice
Trip assignment/ traffic assignment
Trip generation
Trip distribution
Mode choice / model split
Trip/traffic assignment
Number of trips per roadway segment
Standard four-step travel demand model

15. (1) Estimating trip generation
Estimate how many trips a given place will generate regardless of where those trips are destined.
The estimates are based on characteristics of:
Residential households: family size, income, vehicles owned
Nonresidential land uses: number of employees, floor area, retail sales
The zone itself: population density, distance from the central business district

16. (2) Estimating trip distribution
All the trips originated in each zone are distributed among the destinations in other zones.
Zone-to-zone table
Gravity model
Origin
1,000 Trips
4 miles
8 miles
Destination A
20,000 square ft.
10 miles
20,000 42
Trips to A=1,000 x =398
20, , ,000
Destination B
70,000 square ft.
70,000 82
Trips to B=1,000 x =348
20, , ,000
80,000
102
Trips to C=1,000 x =254
Destination C
80,000 square ft.
20, , ,000

17. (3) Estimating model split
Mode choice or model split
Up to this point, each trip is a person trip, undifferentiated by mode.
In this step, the trips are divided between those that use private vehicles on the street system and those that use the public transit system.
Numerous modal split models have been devised over the years; the most popular compare the time and cost of travel between each pair of zones by private vehicle and public transit. Some models also take in account household characteristics, such as vehicle ownership, family size, and family income.

18. (4) Trip assignment
Predict how trips will be distributed between alternate routes from the same origin to the same destination.
The question is resolved by mathematical modeling. Consider that there are two routes, A and B, from zone X to Zone Y. Imagine, also, that we begin by assuming that all traffic takes route A. As travelers shift from A to B, travel times on route A fall while those on route B lengthen. Mathematical models are used to predict when equilibrium will be reached.
The most popular model use a minimum path algorithm, which calculates the route that will incur the least amount of total travel time (including out-of-pocket costs converted to time equivalents) for trip.

19. 3. Limitation of the Four-Step Process
Large-scale home interview surveys in most U.S. cities in 1950s and 1960s, to gain knowledge about the travel patterns of different kinds of households and the relationship between land use and travel behavior. These surveys were very expensive and have rarely been repeated in recent years.
Transportation planners now generally rely on quicker and cheaper methods, such as conducting telephone surveys or having people keep travel diaries.
Questions about work travel have been asked in every decennial census since 1960.
Urban Transportation Planning System (UTPS) – a package of computer program distributed by the Department of Transportation (DOT) of U.S. in the 1970s, performed a particular set of models for the four-step process.

20. 4. Transportation System Management (TSM) Techniques
Improved vehicular flow:
Improvements in signalized intersections
Freeway ramp metering
One-way streets
Removal of on-street parking
Reversible lanes
Traffic channelization
Off-street loading
Transit-stop relocation
Preferential treatment of high-occupancy vehicles:
Freeway bus and carpool (合伙乘车) lanes and access ramps (斜坡)
Bus and carpool lands on city streets and urban arterials
Bus preemption of traffic signals
Toll policies

21. 4. Transportation System Management (TSM) Techniques
Reduced peak-period travel:
Work rescheduling
Congestion pricing
Peak-period truck restriction
Parking management:
Parking regulations
Park-and-ride facilities
Promotion of nonauto or high-occupation auto use:
Ride-sharing
Human-powered travel modes
Auto-restricted zones

22. 4. Transportation System Management (TSM) Techniques
Transit and paratransit service improvements:
Transit marketing
Security measures
Transit shelters
Transit terminals
Transit-fare policies and fare-collection techniques
Extension of transit with paratransit service
Integration of transportation services
Transit management efficiency measures:
Route evaluation
Vehicle communication and monitoring techniques
Maintenance policies
Evaluation of system performance

23. 5. Issues that engage transportation planners
Congestion
Land use
Environmental protection
Financing
Equity
Travelers with special needs

24. （1）Congestion Negative impacts: Psychological impact Monetary costs
Reduce the time that workers can spend at their job
Deprive people of leisure time
Raise the cost of shopping goods
Highly correlated with the frequency of accidents
Greater wear and tear (损耗) on vehicles
More air pollutant emissions and fuel consumption

25. （1）Congestion
Congestion seems to be an inevitable consequence of the clustering of residential and productive activities together in cities.
Supply:
In the short term, planners can increase capacity by widening roadways, reducing impediments to traffic (e.g., by providing left-turn or center lanes), or reducing parking along busy streets.
In the long term, planners can make congestion “pay for itself.”
Overall, local planners have had more success than failure in dealing with specific instances of traffic congestion, but this apparent success sometimes obscure the fact most localized response do not actually reduce traffic congestion but simply move it elsewhere, leaving the large issue of regional congestion for others to solve.

26. （1）Congestion
Demand:
Encourage large employers to provide incentives for their workers to reduce either solo driving (e.g., by carpooling or using alternative modes) or the number of commuting trips they make (e.g., by working at home, telecommuting, or working the same number of hours over fewer days).
Sanctions（制裁）and pricing options
Offering special fares or transfers or allowing some passengers, such as senior citizens, to travel for half fare during noncongested times
Higher parking prices
Congestion pricing
Technological solutions: intelligent transportation systems (ITS)

27. （2）Land use Transportation and development patterns: density
Planners often face two questions:
Can the transportation system be used to produce desired land use patterns?
And if so, what patterns are desirable?
Rail transit advocates
Promoters of neotraditional design – Seaside, Florida
Transit village
Most discussions of the transportation-land use issue avoid two questions:
Technological change:
Today there are more cars than drivers in the United States; thus, because people now have the flexibility offered by the car, new public transit facilities may not substantially affect travel behavior.
Local versus regional impacts
While transportation facilities can have major impacts on small areas, whether they will have regional impacts remains unclear.

28. （3）Environmental protection
Prominent among the externalities (as economists call them) are environmental effects. A related problem is our extravagant appetite for energy. The United States consume more than 18 million barrels of oil a day, more than half of which is imported.
Negative effects of transportation
Smog
Water pollution
Noise pollution
Two basic approaches to the indirect effects of automobile use:
The more conservative is to create regulations that will force technological improvements in the automobile.
The other approach is to try to modify human behavior with the goal of reducing vehicle-miles of travel.
Mass transit use, ride sharing, walking, bicycling, and telecommuting.

29. List of countries by oil consumption bbl: abbreviation of Oil barrel
Rank
Country/Region
Oil - consumption (bbl/day)
Date of information -
World
85,980,000
2008 est. 1
       United States of America
18,690,000
2009 est.
       European Union
13,680,000
2007 est. 2
       China
8,200,000 3
       Japan
4,363,000 4
       India
2,980,000 5
       Russia
2,740,000 6
       Brazil
2,460,000 7
       Germany
2,437,000 8
       Saudi Arabia
2,430,000 9
       Korea, South
2,185,000 10
       Canada
2,151,000

30. （4）Financing
There is always stronger support for new facilities, maintenance and repairs tend to be slighted: the severe deterioration of many highways and bridges is evidence of years of negelct.
There is an established structure for financing highway construction.
On average, farebox revenues amount to about 40 percent of operating cost in the United States.
With the Urban Mass Transportation Act of 1964, the federal government began making grants to local governments for public transportation.
Currently, the federal government pays up to 80 percent of capital costs and up to 50 percent of operating losses.
Subsidies for public transit – mostly by state and local governments
A portion of fuel tax revenues
The most popular source – local sales tax
Sometimes the voters approve the tax by referendum.
Public transit and the labor unions

31. （5）Equity Low-income families Households without cars
Inner-city residents
Captive riders被动乘坐者
Reverse commute反向交通
Well-designed transit services or greater car ownership as a way to deal with the intractable transportation problems facing poor families?

32. （6）Travelers with special needs
Elderly people (over 65)
People with disabilities
Americans with Disabilities Act (ADA) of 1990
Specific obligations for transit systems: all new buses must be accessible – that is, equipped with a ramp or a lift to accommodate wheelchairs – and all systems must provide paratransit services that take passengers directly from their home to their destinations for those individuals who are unable to use fixed-route services.
Dilemma to transportation planners:
Licensing is almost universal among both men and women over 70.
On one hand, the growing number of older drivers creates safety problems; on the other hand, it is desirable for older people to be as independent as possible for as long as possible.

33. CONGESTION EXTERNALITIES
According to the Texas Transportation Institute, the typical U.S. commuter in 2003 wasted about 47 hours because of traffic congestion. In some cities, the time lost by the typical commuter is much higher: 93 hours in Los Angeles, 72 hours in San Francisco, 69 hours in Washington DC, 67 hours in Atlanta, and 63 hours in Houston.
In addition to time lost, $5 billion worth of gasoline and diesel fuel is wasted each year because of delays and slow travel. Adding the value of lost time to the wasted fuel, the annual cost is $63 billion per year. This is about five times the congestion cost experienced in 1982.

34. Congestion Externalities and the Congestion Tax

35. Benefits and Costs of the Congestion Tax
People who pay the tax and continue to use the highway
Decrease in time cost. The tax decreases traffic volume, so travel speed increases and travel time decreases.
Lower income tax. The government can use the revenue from the congestion tax to cut other local taxes, so the congestion tax is revenue-neutral.
People who don’t use the roadway after the congestion tax is imposed
Lower income tax.
Loss of consumer surplus.

36. Estimates of Congestion Taxes
The efficient congestion tax varies across space and time.
According to Parry and Small (2009), for U.S. metropolitan areas as a whole, the efficient tax in 2005 was about $0.056 per mile. The efficient tax is higher for peak-period travel: $0.085 per mile.
These overall averages obscure substantial differences across metropolitan areas in the efficient congestion tax.

37. Congestion Taxes in Selected Metropolitan Areas
The Table shows estimated congestion taxes for three metropolitan areas, Washington DC, Los Angeles, and London. For the peak travel period, the tax per mile is $0.21 in Washington, $0.26 in Los Angeles, and $1.23 in London. As expected, the off-peak taxes are lower. In highly congested London, the difference in traffic volumes between peak and off-peak travel is relatively small, so the off-peak tax is $0.49 per mile.

38. London Congestion Charge, Old Street, England

39. London Congestion Charge Zone

40. Signs and Cameras for Congestion Charge
Signs indicate the boundary of the congestion charge area
Congestion charge CCTV (Closed-Circuit Television) cameras on Vauxhall Bridge Road

41. Congestion Charge in London
The standard fee for applicable vehicles is £10 per day if paid by midnight on the day of travel, £12 if paid by the end of the following day, or £9 if registered with CC Autopay.
Businesses with ten or more vehicles can register with TfL (Transport for London), and will be charged £9 per vehicle per day for each vehicle detected within the zone.
Failure to pay results in a fine of £120, reduced to £60 if paid within 14 days, but increased to £187 if unpaid after 28 days.

42. Congestion Charge in London
Registered cars which emit 100g/km or less of carbon dioxide and meet the Euro 5 standard, vehicles with 9 or more seats, motor-tricycles, accredited breakdown companies and roadside recovery vehicles receive 100% discounts.
Refunds are available to people who pay monthly or annual in advance whose plans change; reimbursements are available to NHS (National Health Service) patients assessed to be too ill to travel by public transport, NHS staff using vehicles on official business and fire fighters. Residents living within or very close to the zone are eligible for a 90% discount which is charged via CC Autopay (Congestion Charge Autopay).

43. Congestion Charge in London
In November 2012 Transport for London(TfL) presented a proposal to abolish the Greener Vehicle Discount starting in July Instead, a new Ultra Low Emission Discount scheme would be introduced with more stringent emission standards that would limit the free access to the congestion charge zone to electric cars and some hybrids.
As of November 2012, more than 19,000 vehicles, mainly with small diesel engines, avoid the charge because their engines produce emissions of less than 100g per km of CO2. Owners of those cars will be granted a two-year sunset period before they are made to pay the full congestion charge.
The plan is still subject to the approval of Mayor Boris Johnson, and is currently undergoing a 12-week public consultation that closes on 8 February 2013.

44. Implementing Road Pricing: Tolls
Modern technology allows the efficient and convenient collection of taxes for using congested roads.
Under a vehicle identification system (VIS), each car is equipped with a transponder—an electronic device that allows sensors along the road to identify a car as it passes. The system records the number of times a vehicle uses a congested highway and sends a congestion bill to the driver at the end of the month.

45. Implementing Road Pricing: Tolls
Singapore was the first city to use prices to control the volume of traffic. Under the Area Licensing System (ALS) implemented in 1975, drivers were charged about $2 per day to travel in a toll zone in the central area of the city.
In 1998, Singapore switched to Electronic Road Pricing (ERP), a smart-card system with charges that increase with the level of congestion. The system features gantries that charge users for entering the central area during the daytime, and 14 tolled highways that are subject to tolls during the morning peak period. There are no charges for travel on the weekends.

46. ERP gantry at North Bridge Road

47. Electronic Road Pricing in Singapore
The scheme consists of ERP gantries located at all roads linking into Singapore's central business district – areas within the Central Area such as the Downtown Core. They are also located along the expressways and arterial roads with heavy traffic to discourage usage during peak hours.
The gantry system is actually a system of sensors on 2 gantries, one in front of the other. Cameras are also attached to the gantries to capture the rear license plate numbers of vehicles. Currently, there are 80 ERP gantries in Singapore. New gantries are implemented where congestion is severe, like expressways and other roads.

48. Electronic Road Pricing in Singapore
A device known as an In-vehicle Unit (IU) is affixed on the lower right corner of the front windscreen within sight of the driver, in which a stored-value card, the CashCard, is inserted for payment of the road usage charges. The second generation IU accepts Contactless NETS CashCard and EZ-Link. The cost of an IU is S$150. It is mandatory for all Singapore-registered vehicles to be fitted with an IU if they wish to use the priced roads.

49. Electronic Road Pricing in Singapore
The charge passing through a gantry depends on the location and time, the peak hour being the most expensive.
Examples include a trip from Woodlands to Raffles Place via Yishun – CTE – CBD will cost about S$15 during peak as the driver will pass about 5 gantries, whereas during lunchtime, it will cost about S$2.
Foreigners driving foreign-registered cars on priced roads, during the ERP operating hours, could choose to either rent an IU or pay a daily flat fee of S$5 when leaving Singapore.

50. Electronic Road Pricing in Singapore
If a vehicle owner does not have sufficient value in their CashCard (or EZ-Link) when passing through an ERP, the owner receives a fine by post within two weeks. The violator must pay the ERP charges plus a $10 administration fee within two weeks of the notice. Online payment is allowed; listing just the Vehicle Registration Number is required. Otherwise, a penalty of S$70 is issued by registered post to the vehicle owner, which rises to S$1000, or one month in jail, if not settled within 30 days.

51. Milan Area C
Area C gate in Porta Ticinese
Area C sign

52. Milan Area C
Area C traffic restricted zone (ZTL)

53. Milan Area C
Area C is a congestion charge introduced in Milan, Italy, on January 16, 2012, replacing the previous pollution charge Ecopass and based on the same designated traffic restricted zone or ZTL (Italian: Zona a Traffico Limitato), corresponding to the central Cerchia dei Bastioni area.
The ZTL encompasses about 8.2 km2 (3.2 sq mi) and 77,000 residents (4.5% and 6% of the city total, respectively). The area is accessible through 43 gates, monitored by video cameras.
Area C is as an 18-month pilot program based on the partial implementation of the results of a referendum that took place on June The objective of the program is to drastically reduce the chronic traffic jams that take place in the city of Milan, to promote sustainable mobility and public transport, and to decrease the existing levels of smog that have become unsustainable from the point of view of public health.

54. Milan Area C
The program was temporarily suspended from 25 July due to a ruling by the Council of State after protests by parking owners in the center of Milan. Area C was reintroduced on 17 September.
The charge applies to every vehicle entering the city centre on weekdays (except Saturday) from 7:30 am to 7:30 pm. Every vehicle entering the charging zone must pay €5 regardless of its pollution level. Residents inside the area have 40 free accesses per year and a discounted fare of €2.
Access to the area is forbidden for diesel Euro 3 or below, gasoline Euro 0 and private vehicles over 7 m (23 ft) long. Electric vehicles, motorcycles and scooters, public utilities' vehicles, police and emergency vehicles, buses and taxis are exempt from the charge. Hybrid electric and bi-fuel natural gas vehicles (CNG and LPG) are exempt until 1 January 2013.
After the suspension in summer 2012, the entrance in the area is free from 6 pm on Thursday.

55. Congestion Charge in Milan Area C
Engine class → Euro levels →
Gasoline
Diesel
Hybrid / bi-fuel
Electric
Scooters 5 4 3 2 1
non-residents €5
banned
free1
free
residents2 €2
commercial €3 NA
public service3
banned4
1. until residents have also 40 free accesses per year 3. includes public transport, emergency vehicles, taxis 4. with exceptions

56. Early Results
A comparison between vehicles entering Milan city center on average per weekday with Ecopass pollution charge (2011) and Area C congestion charge (2012). Weeks from 16 January to 30 September. The program was suspended during weeks 29 to 35. Data from Comune di Milano
Pollution: no significant change.
As of 30 April, the traffic reduction inside Area C restricted area since its implementation, compared to the same period of the previous year:
Traffic reduction inside Area C restricted area: 34.3%.
The total traffic reduction in the Milan area was about 7%.

57. Implementing Road Pricing: HOT Lanes
Many U.S. cities have designated highway lanes for use by high-occupancy vehicles—buses and carpools (two or more riders).
The idea behind an HOV (high-occupancy vehicle) lane is to encourage carpooling, but if not many solo drivers switch to carpooling or buses, the HOV lane will be underutilized and the other lanes will become more congested.
A recent response to this problem is to designate lanes for use by either high-occupancy vehicles or solo drivers who are willing to pay a toll. These express lanes or HOT lanes (for high-occupancy or toll) are used in Los Angeles, San Diego, Houston, and Minneapolis-St. Paul, and are under consideration in many other cities.

58. Implementing Road Pricing: HOT Lanes
In San Diego, the toll varies with the level of congestion in order to maintain a target speed. The toll is typically between $0.50 and $4.00, but has been as high as $8.00 (Small and Verhoef, 2007).
The use of HOT lanes is relatively high for commuters, high-income people, highly educated people, women, and people between 35 and 45 years of age.

59. Implementing Road Pricing: HOT Lanes
There are important trade-offs in pricing express lanes. If the price is relatively high, the express volume will be relatively low, and congestion in the other lanes will be relatively high, as in the case of a traditional HOV lane.
As the price of the express lane decreases, some travelers will switch to the express lane, decreasing congestion in the regular lanes.
In general, an express lane sorts travelers with respect to their willingness to pay for speed: travelers with a relatively high opportunity cost of travel time will use the express lane, while those with a relatively low opportunity cost will use the slower regular lane.

60. Implementing Road Pricing: HOT Lanes
A recent study explored the effects of express lanes in Orange County, California (Small, Winston, and Yan, 2005, 2006).
A 10-mile stretch of State Route 91 has four regular lanes and two express lanes in each direction. The toll for the express lanes varies with traffic volume, and there are discounts for carpools.
During the study, the peak toll was $3.30, and the average time saved for a 10-mile trip in the express lane was about 3.4 minutes.

61. Implementing Road Pricing: HOT Lanes
The choices of the travelers revealed the following.
Travelers vary in time cost of travel, with a median value of $21.46 per hour, or about 93 percent of the average wage rate.
The price elasticity of demand for the express lane is –1.59: a 10 percent increase in price decreases the number of travelers using the express lane by 15.9 percent.
The elasticity of demand with respect to travel time in the regular (free) lanes is 0.73: a 10 percent increase in travel time increases the number of express travelers by 7.3 percent.

62. ALTERNATIVES TO A CONGESTION TAX
Modal substitution.
The tax increases the cost of single-driver travel relative to carpooling and mass transit (buses, subways, light rail), causing some travelers to switch to other travel modes.
Time of travel.
The tax is highest during the peak travel periods, causing some travelers to travel at different times. Because work and school schedules are relatively inflexible, commuters and students would be less likely to change their travel times than other travelers (e.g., shoppers). Nonetheless, firms would have an incentive to change work schedules to allow their workers to avoid costly travel during the peak periods.

63. ALTERNATIVES TO A CONGESTION TAX
Travel route.
The congestion tax is highest on the most congested routes, causing some travelers to switch to alternative routes.
Location choices.
The congestion tax increases the unit cost of travel (travel cost per mile), causing some commuters to decrease their commuting distances. Some workers may move closer to their jobs, and others may switch to jobs closer to their residences.

64. Gasoline Tax
One alternative to the congestion tax is a gasoline tax. The simple idea is that if the cost per mile of travel increases, people will drive less.
The problem is that a gas tax increases the cost of all automobile travel, not just travel along congested routes during peak periods.
A gas tax decreases the relative cost of alternative travel modes, causing modal substitution in the right direction (#1 above). It also increases the cost per mile traveled, affecting location choice in the right direction (#4). But the gas tax fails to affect the time of travel or the travel route (#2 and #3), except to the extent that congestion generates lower gas mileage.

65. Gasoline Tax
It may be tempting to conclude that getting two responses (mode and location) out of four isn’t so bad. But consider the gasoline tax required to internalize congestion externality for peak-period congestion. If the appropriate congestion tax is $0.21 per mile and the average vehicle gets 20 miles per gallon of gasoline, the required gas tax would be $4.20 per gallon.
The problem is that the tax would apply to all gasoline purchased, not just the gasoline used during the peak period on congested roads. There are some environmental benefits from taxing gasoline, but the appropriate tax is much less than $4.20 per gallon.
It is worth noting that a tax of $4.20 would cause the price of gasoline in the United States to be close to the prices in several countries in Western Europe.

66. Subsidies for Transit
Another alternative to a congestion tax is to subsidize mass transit. The basic idea is to match the underpricing of car travel with equivalent underpricing of buses, subways, commuter trains, and light rail.
Transit subsidies change modal choice (#1) in the right direction but don’t directly affect the time of travel, travel routes, or location choice.
Although a transit subsidy will decrease the volume of automobile travel and reduce congestion, it will never be as efficient as a congestion tax. A fundamental problem of a matching subsidy is that it causes transportation in general to be underpriced, leading to excessive amounts of travel.

67. The Pricing of Parking
The conventional pricing of workplace parking generates a relatively low cost of driving to work.
Many firms provide free parking to their employees: a firm absorbs the cost of parking facilities as a cost of doing business. An alternative approach is to charge employees for parking, and to use the money raised in parking fees to increase the wages of all workers, including workers who carpool, ride mass transit, walk, or bike. This approach, known as “cashing out” free parking, increases the cost of driving to work and encourages workers to use alternative commuting modes.
In the figure, eliminating this price distortion would shift the demand curve for solo driving to the left, decreasing the equilibrium traffic volume and decreasing the cost associated with congestion.

68. The Pricing of Parking
There is evidence that commuters respond to changes in the price of parking.
Shoup (1998) estimates that employer-paid parking shifts 25 percent of all commuters into solo driving and increases the number of cars driven to work by 19 percent.
At four workplaces in Los Angeles that eliminated free parking, the number of solo drivers decreased by 19 percent to 81 percent (Small and Verhoef, 2007). In case studies of the effect of a law requiring California employers to cash out free parking, the number of solo drivers decreased by an average of 17 percent.

69. The Pricing of Parking
What is the actual social cost of parking in urban areas?
Small and Verhoef (2007) estimate the daily cost of commuter parking for different sites in a metropolitan area. The estimated daily cost is $4.44 for a suburban surface lot, $9.18 for a suburban structure, and $15.04 for an urban structure.
Based on the suburban figures, they estimate that the commuter parking cost per mile traveled is $0.28. The cost per mile is relatively large because (a) the opportunity cost of land used for commuter parking is relatively high, and (b) the fixed cost of commuter parking lots and structures are spread over commuting trips, not all trips.