commodities are expected to be among the first commodity types that might shift their mode of transport to faster modes. This is because the time value of these commodities is typically higher than low-value bulk commodities.

Moreover, Avetisyan (2018) studied the impact of a global carbon tax of 27.3 USD/ton CO2 applied to transport sectors of all modes (i.e. industry sectors which provide transportation services) on modal choices of shippers globally. The study concluded that under a scenario, based on trade data from 2011, where a global carbon tax is applied to all transport modes, the transport of high-value products (e.g. microchips and seeds) would shift to maritime transport from air transport, while the transport for bulky products (e.g. paddy rice, wheat, and cereal grains) would shift to maritime transport from other (land-based) transport modes (rail, road).

**Table 1:** Impact of 100% increase in maritime transport costs and 65% speed reduction on global modal share of international freight transport by 2030 (source: (Halim et al., 2018))

||**Baseline**<br>**2030 (Mt)**|**Share**<br>**(%)**|**100% increase**<br>**in maritime**<br>**transport cost**<br>**and 65% speed**<br>**reduction(Mt)**|**Share**<br>**(%)**|**Difference**<br>**in share (%)**|**Difference in**<br>**weights (Mt)**|
|---|---|---|---|---|---|---|
|**Air**|70|0.33|72|0.34|0.01|2.60|
|**Rail**|598|2.84|611|2.90|0.06|13.17|
|**Road**|2,539|12.06|2,557|12.15|0.09|17.92|
|**Sea**|17,813|84.65|17,780|84.49|-0.16|-33.70|
|**Waterways **|22|0.11|22|0.11|0.00|0.01|

From the references above, it can be deduced that increased transport costs would have a marginal effect on modal shifts in global freight transport. However, the scale of this impact, as exemplified by China-Europe case, can vary from regionally depending on the characteristics of transportation networks.

# **2. Impact on route and port choice**

There are few studies that focus on the impact of mitigation measures on route and port choice (Tavasszy et al. (2016). In general, the effect of changes in shippers’ routing decision can be driven by two mechanisms. First, changes in the spatial patterns of trade between States due to new trade relationships may change the position of transit ports. Second, the application of mitigation measures might increase transport costs of each route to various degrees. Routes that are longer but cheaper due to, for instance, a hub and spoke structure may no longer be cheapest after GHG mitigation measures are applied. Shippers will switch to cheaper routes based on these changes in transport costs.

In the study, they found that the application of a carbon price of up to 49 USD/ton CO2 by 2040 could lead on average to a 0.5% decrease in the annual container throughput of ports worldwide. The decrease is not uniform across different commodity types. For example, coal is the most affected commodity with a 4.3% decrease, followed by agriculture (3.1%), and construction materials (0.7%). However, the study does not detail the impact of changes in shippers’ routing decisions on port throughput. Further investigation is needed to assess the potential impacts of changes in route choice of shippers on port traffic worldwide.

Another study conducted by (Tavasszy et al., 2011) presents a scenario where a drastic reduction in ship operational speed (14-15 knots instead of 22-24 knots) is implemented by global shipping companies. Also called slow steaming, this can be done 11