In 2019 we submitted our science based targets (SBT) to the Science Based Target initiative (SBTi) for review and approval. The SBTi confirmed that our targets, which we set in 2018 with the aim of decarbonising our business towards 2030, contribute to achieving the Paris Climate Agreement. These targets include our aim to reduce CO2 emissions across all our operations, including outsourced road and air transport.
During the year we successfully issued a €300 million Green Bond. The proceeds will be used during the seven-year bond period to support our sustainability goals of becoming an emission-free last-mile delivery service provider in the Benelux by 2030. We also introduced two new KPIs, aimed at driving our emission-free deliveries. The first measures our share of emission-free delivery of parcels and letters in the last-mile in the Benelux. The second measures the reduction of CO2 emissions per km we have achieved, compared to our 2017 base year. We monitored our progress compared to 2018 and developed an action plan aimed at increasing the share of emission-free kilometres.
We have started to monitor progress on our relative CO2 emissions per kilometre for all our own operations, compared to the baseline year 2017. And we have developed a detailed action plan to meet our long-term target of an 80% reduction in our relative impact by 2030 compared to 2017.
However, since 2017 we have faced a number of challenges in this area, mainly related to the extension of lease contracts and the lack of availability of low-emission vehicles with the right specifications for our operations. In 2019, this resulted in a 6% increase in our CO2 emissions per kilometre compared to 2018, and an 8% increase compared to our 2017 base year.
To overcome these issues, we are initially looking into scaling up the use of sustainable fuels, which for diesel and liquefied natural gas (LNG) are only just starting to become available on a large scale. Looking further ahead, we expect to make significant steps towards the electrification of our car fleet, which we expect to result in major improvements in around five years time.
In 2019, 19% of our last-mile kilometres related to the delivery of mail and parcels were transported emission-free. This includes the relevant kilometres of our delivery partners. This is a slight improvement compared to 2018, as we started to phase in electric vehicles across our fleet on a small scale, increased our e-bike logistics and expanded our fleet of electric scooters. We foresee marginal improvements in the coming years as we prepare our infrastructure and test the use of electric vehicles in our operations. Although we plan to scale up our electric fleet as soon as we can, we expect to see a large-scale transition across our own fleet and those of our delivery partners starting in 2025.
To support our emission-free journey, in 2019 we introduced Zero 2030, a programme consisting of specific projects that contribute to us reaching our 2030 goal. For each project, we detail the short- and long-term environmental benefits and actions. These include specific goals set for individual parts of the business and general company-wide targets. We also launched and began to develop more than 40 different initiatives covering our main networks. We monitor progress and steer on our zeros to achieve our goals.
In relation to our goals on sustainable city logistics, we operate electric distribution from three of our parcel sorting and delivery centres, and have expanded our City Logistics programme, with (e)-bike delivery taking place in 12 cities across the Netherlands. For 2020, we are introducing a KPI on sustainable city logistics linked to the percentage of city centres we deliver to emission-free, based on our goal of 25 city centres by 2025.
In 2019 PostNL was again ranked in the top-three sustainable companies worldwide in the transport and logistics sector by the Dow Jones Sustainability Index (DJSI). This benchmark evaluates listed companies on economic, social and environmental transparency and performance.
We steer on our strategy through our relevant drivers, as explained in the chapter 'Our strategy'. In this chapter we explain how our drivers help us achieve our strategic objective, which is to reduce our environmental impact. For each driver we provide examples that illustrate the events, initiatives and related outputs that contributed to our performance.