Difference between revisions of "Composite traffic"

To make the construction of Route matrix as simple as possible for a new city, the roads are defined in the following way. First, the whole metropolitan are is divided into 15 regions, and these regions are further divided into 129 areas with 7300 inhabitants on average. The 129 areas are standard areas for urban planning, but the regions were formed for this particular purpose. The criteria for forming a region were that they

1. are exclusive and mutually exhaustive
2. are as large as possible without creating very unrealistic routes between areas. Routes are defined in a way that between any two regions, there is only one specific road that is used to cross the region borders (and travel the distance between the regions if they are not neighbours).

It is thus necessary to describe the routes between all areas within each region, and the routes between all regions. However, then it is possible to deduce the detailed routes between two areas that are in different regions using these hierarchical instructions.

The routes are described as lists of areas that are along the road between the origin and destination. The route description needs not be in full detail if the details between two areas are defined in Roads node. A minimum number of existing roads were selected so that the routes in the model would not be very unrealistic. This work was done manually with a map. Note that the absolute numbers of 'Average vehicle flow on the 30 most busy roads' are likely biased upwards because all traffic from smaller streets is packed to the major roads in the model.

• Routes outside
• Routes inside
• Roads
• Area name

• In-area distance
• Link length

The total number of trips equals the number of car trips in Helsinki area on a working day in 2000. All scenarios have the same street strucure and number of trips with a particular origin, destination, and time. The trips are divided into car trips and composite trips differently in each scenario based on two variables. Composite fraction is the percentage of the trips that are handled by composite traffic; the remaining trips are handled by personal cars. Guaranteed area defines the area where composite traffic is provided (i.e. the area where you are guaranteed to get a composite vehicle if you want one). The default assumption is that both the origin AND the destination must be in the guaranteed area, but it is also easy to evaluate scenarios where the guarantee covers all trips in the Helsinki area as long as either the origin OR the destination is in the guaranteed area.

The model calculates the expected number of trips for each origin-destination-time cell, and picks one random number from Poisson distributioin based on the expectation. After that, the model is deterministic all the way to Outputs node.

• Total trips
• Population
• Areal surface
• HLT2004-2005 (Traffic study in Helsinki)
• Workplaces
• Inhabitants
• Time in traffic
• Trips per municipality
• Trips per place
• Trips per place and mode

The composite traffic trips are allocated into different vehicles. The following hierarchy is used in allocation. If the criterion is fulfilled, that number of passengers is allocated, and the rest will go to the next criterion. The criteria are used for a group of trips that has the same origin, destination, and time. Time resolution is 12 min. Origin and destination are described as '129-areas' used for city authorities in Helsinki metropolitan area. The 129 areas have on average 7300 inhabitants (0, 25%, 50%, 75%, and 100% percentiles are 0, 3400, 6800, 10300, and 28300, respectively).

1. Use an 8-seat vehicle if there are enough passengers to get it full.
2. Use a 4-seat vehicle if there are enough passengers to get it full. Divide the trips into two parts so that the passengers change vehicle in the most busy point along the route. Then,
3. Use an 8-seat vehicle if there are enough passengers to get it full.
4. Use a 4-seat vehicle if there are enough passengers to get it full.
5. Use a 4-seat vehicle for all remaining trips.

The criterion is checked at the actual arrival time at the transfer point, i.e. the model takes into account the different travel times between areas.

The following outputs are calculated:

• Number of passenger trips by mode (car or composite traffic)
• Number of passenger trips by vehicle type. Note that in this output, the trip that includes a transfer is calculated twice.
• Vehicle kilometres driven
• Parking lots needed for the vehicles that are used
• Average vehicle numbers per hour for the 30 most busy links at 8.00-9.00 in the morning
• Number of vehicles needed
• Waiting time due to traffic jams and waiting for composite vehicle to arrive.

The outputs of each scenario are indexed (when relevant) by period (day, evening, night); zone (Helsinki downtown, other centre, suburb), length of trip (less or more than 5 km), and vehicle type (8-seat or 4-seat vehicle with of without transfer, or car).

• Drop length (how many additional minutes does it take for a composite vehicle to stop once more to drop off passengers).
• Drop points (number of drop points in each area).

Costs are separately calculated for the passenger and the society. Some costs affect these stakeholders differently, such as fine particle and carbon dioxide emissions: they are calculated as societal costs only, not as costs to a passenger.

The following endpoints are considered (see Table 1):

• Fraction of composite trips without change (%)
• Vehicles needed (number)
• Parking places need (number)
• Average vehicle flow on the 30 most busy roads (vehicles/h at 8.00-9.00 AM)
• Fine particle (<2.5 µm of diameter) emissions (kg per day)
• Carbon dioxide emissions (ton per day)
• Driver salaries (thousand e per day)
• Vehicle capital and operational costs (thousand e per day)
• Time cost (thousand e per day)
• Average car trip cost to passenger (e per trip)
• Expected composite trip cost to passenger (e per trip)

The following costs are taken into account for passenger (P) or societal (S) costs:

• Vehicle capital cost (P+S)
• Driver salary cost (P+S)
• Driving cost (fuel) (P+S)
• Parking (parking fees for individual drivers) (P)
• Parking land (opportunity cost of reserving land to parking purposes) (P+S)
• Emissions (fine particles and carbon dioxide causing health and climate change effects, respectively (S)
• Time for waiting composite vahicles, time spent in traffic jams (P+S)
• Accidents (an option only, not used in the current model)
• Ticket (profit for composite service provider) (P)

The module has a submodule Cost elements. It contains the detailed descriptions of the unit costs and other input variables that are used to calculate the pressures of each scenario. The values used are dependent on the stakeholder. For example, the car price is the price that a random new car would cost, and it has therefore large uncertainty. On the other hand, the price of a 4-seat composite vehicle is the average price a taxi-style car would cost in Finland, and the confidence intervals are narrower because there is no individual uncertainty. This is because the price of an individual car affects the costs of individual car trips, while the cost of composite trip is dependent on the total cost of vehicles.

Variation between individuals has been separately estimated for three variables: how passengers evaluate the capital costs of owning a car; how passengers are willing to pay for either the right to drive themselves or to not need to drive; and how many passengers are traveling together.

• Scenario data
• Scenario description

• Vehicle price
• Fuel consumption
• Fuel price
• Car maintenance
• Car occupancy
• Driver salary
• Vehicle lifetime
• PM unit lethality
• Emission unit cost
• Parking space
• Group size
• Rush delay
• Trips per car
• Ticket
• Time unit cost
• Parking price
• Accident costs
• Accidents
• Emission factor