Network for Transport Measures

5.7 Calculation method issues

Methods and manuals > 5. Road cargo transport > Wikis > 5.7 Calculation method issues

Distances

Direct transport – frequent shipments

The distance for a direct transport between two addresses carried out by one vehicle can be found in NTMCalc.

Pre-positioning

The truck must usually be positioned empty before the transport. NTM suggests that

  • the emissions related to the positioning trip BEFORE the transport is calculated and added to the emissions from the vehicle during the actual transport
  • The emissions related to empty running after delivery of the investigated cargo is not considered, unless the vehicle operates in a shuttle system, see example below.

If no information on pre-positioning distances is available, a factor of 20% of the transport distance could be used for calculating the positioning distance. Note that the emissions for the return distance should be calculated with fuel consumption data for an empty vehicle.

Back haul / return loads

There will sometimes be return loads from the primary cargo delivery adress to consider (e.g. distribution of beverages in glass return bottles). NTM suggests that this load is made to bear all the environmental performance data (i.e. emissions etc.) for the truck on the return trip. The argument for this is the more simple approach with no allocation between the primary load and the return cargo.

As a special example, the case of a ‘one-way’ shuttle system with dedicated vehicles (i.e. tankers for fuels, chemicals and food stuffs) will show a 50% capacity utilisation (100% load capacity utilisation outbound, 0% on the return trip).

Note that the emissions for the return distance in this case should be calculated with fuel consumption data for the empty vehicle.

Direct transport – single shipment

The case of a direct transport with a singular shipment (i.e. not frequent and forseeable) will be handled similar to the frequent shipments. The singular nature of such a transport will, however, decrease the possibility to achieve a) a high degree of load capacity utilisation on the outbound trip (i.e. selection of the optimal vehicle and adoption to the nature of the cargo is usually not possible) and b) short positioning distances.

NTM suggests that, if no situation-specific data is available, a positioning distance equal to 50%[1] of the transported distance is used. Note that the emissions for this distance should be calculated with fuel consumption data for the empty vehicle.

The emissions for the empty vehicle after delivery of the cargo should not be considered, unless this simplification seems unreasonable, eg. for a delivery to a remote construction site etc.

Transport via integrating terminals

When a shipment is transported in an integrated transport system, the actual route taken by the cargo will not be known by the shipper. The transport will be routed via one or more terminals usually not located along the shortest route between A-B. The idea behind this system is to compensate the increased transport distance by achieving higher load capacity utilisation of the vehicles, especially on the longer route. A typical transport of a shipment could be composed of the following stages:

Pick-up and transport to terminal 1 by a truck on a pick-up route

  1. At terminal 1: cargo is unloaded and integrated with other cargo going to the same destination area. The shipment is loaded, integrated with other shipments, onto a truck (or rail car) going to terminal 2.
  2. At terminal 2: the shipment is unloaded and integrated with other cargo going to customers in the same area. The cargo is then loaded onto a distribution truck and transported to the consignee in a distribution route.

The cargo will in this system (almost) always travel a longer distance than would the cargo be transported by a dedicated truck driving the shortest route between the shipper and receiver. It can be very difficult (even for the integrating company!) to find the actual distance travelled by the cargo in the different steps, especially during the pick-up and delivery. The capacity utilisation of the different vehicles used in the system is also difficult to monitor.

The most accurate ‘actual distance’ data available will as always be obtained from the integrator, or his/her sub-contracted haulier/vehicle operator. However, if no data is available from the integrator, NTM suggests the following simplified calculation method for cargo transported in integrated transport systems.

  1. Find the road distance between the two major city centers nearby the origin and destination of the cargo. Assume that the cargo is transported on a semi-trailer between these locations (truck and trailer in SE + FI). Use default capacity utilisation described in section on vehicle types.
  2. Find the road distance between the origin/destination and the closest city center (where the theoretical integration/distribution terminal is assumed to be located). Assume that a medium-sized duty vehicle (no. 4 or 5) is used for the delivery transport to the reciever. Use default capacity utilisation described in section on vehicle types.

 

Method for allocation of environmental performance to analysed cargo

The basic assumption in the NTM allocation principle is that all emissions from the transport vehicles, during transport and empty positioning/return transports) must be allocated to the transported cargo.

The emission related to the transport of a specific shipment is then found by calculating its relative share of the total cargo load.

The standard option is to allocate the emissions to the shipment/investigated cargo by its physical weight (w(phys)). The total weight of the carried cargo (W(phys)), if not known, can be calculated as the product of the (maximum) load capacity (LCweight(phys)) and the weight- based load capacity utilisation (LCUweight(phys)); see Equation below:

Allocation equation

Equation for calculating total emission of substance i for driving on road x with vehicle y

 

Although weight is the most common unit for cargo measurements, other units for measurements of the amount of cargo could be more suitable (e.g. units such as pallet positions, TEU, cubic metre and load metre). The weight of cargo with low density is usually converted into a ‘volumetric or dimensional weight’ based on a standard density conversion factor; see integrated transport systems below.

As shown in Equation  above, the default value of the cargo weight can be found by multiplying the max load capacity by the capacity utilisation. Default values for the capacity utilisation are suggested in Road cargo vehicle types wiki when no specific data can be obtained.

Integrated transport systems

Integrated transport systems are used for all kinds of shipments and cargo types. In order to achieve a fair pricing of each shipment’s share of the vehicle load capacity, the volumetric weight method is frequently applied. The volumetric weight, sometimes called the dimensional (or dim) weight, is the weight obtained as the commercial calculation factor [kg/m3] is multiplied by the volume [m3] of the shipment, yielding a factious weight measure (w(dim)). The physical and volumetric weights for each shipment are then compared, and the largest is used for the calculation of price and environmental load. The dim, or volumetric, weight is thus used for shipments with a density below the commercial calculation factor, which is usually set to 333 [kg/m3] for European road transport and 280 [kg/m3] for national Swedish road transport.

The load capacity utilisation for the integrated transport system is then calculated by dividing the dimensional weight (w(dim)), by the actual carrying capacity, yielding a higher capacity utilisation than would the physical weight be used.

This method is chosen since the dim-weight better reflects the actual load capacity utilisation of the vehicle.

The capacity utilisation varies between different companies, regions, seasons etc. and  that is why it is important to seek for specific data for the investigated cargo.

If no specific data can be obtained, NTM suggests the use capacity utilisation are suggested in Road cargo vehicle types wiki for load capacity utilisation for integrated transport systems, in combination with the dimensional weight for the investigated shipment:

  • 50% of max physical weight capacity (LC) of the vehicles employed in pick-up and delivery to/from the integrating terminals, combined with direct distance to terminal
  • 70% of max physical weight capacity (LC) of vehicle employed between terminals

Being the only available data on utilisation, the capacity utilisation based on the dimensional weight should also be applied in the calculation of the vehicle fuel consumption; see fuel road cargo wiki onconsumption. Since the dimensional weight always is larger than the physical weight (w(dim) > w(phys)), this will lead to a slight overestimation of the fuel consumption for the lorries in this kind of traffic. The error introduced in this way contributes to the suggested low and high uncertainty limits.

Direct transport – frequent shipments

NTM suggests the use of a utilisation degree of 75% of max load capacity when carrying cargo too the reciever. One must also include the emissions from the positioning distance. Use the unit that best describes the use of the load capacity of the vehicle in the allocation calculation.

Direct transport – single shipments

NTM suggests the use of a utilisation degree of 50% of max load capacity when carrying cargo too the reciever. One must also include the emissions from the positioning distance. Use the unit that best describes the use of the load capacity of the vehicle in the allocation calculation.

If no information besides vehicle type is known about the transport, the default data capacity utilisation suggested in Road cargo vehicle types wiki should be applied.

The NTM data values are not supported by any research or statistical analysis. The data originates from approximations for Swedish domestic conditions made by members in NTM work groupe ‘Goods and Logistics’ (mainly by integrators, using the volumetric (or dim) weight for analyzed cargo with low density). The data for swedish truck transport presented in road cargo wiki on vehicle types is approximate values extracted from  ARTEMIS (2008). This data differs from the suggested NTM data mainly in terms of a broader coverage of cargo types, i.e. all types of cargo is considered. The suggested NTM data is mainly based on integrated transport systems handling pallet goods.

NTM points out the urgent need to investigate the typical/average positioning distances and load capacity utilisation degrees of the selected vehicles when employed in the different transport situations. The data presented in Road cargo wiki on vehicle types  must therefore only be used in screening analyses.

Uncertainties – low, average and high value

The uncertainty in the calculation is indicated by presenting data for a typical transport together with a suggested high and low value. The span is intended to include all different impact factors influencing the fuel consumption and emission profile. The span is created by varying the fuel consumption, keeping all other variables constant (load factor, emission profile). NTM suggests that the span is created by alternating the fuel consumption by -10% (low estimate) and +30 or 40 % (high estimate).

 

[1] This rather high positioning distance is suggested in order to encourage operators to obtain more situation specific data.