Dáil Éireann Debate, Wednesday - 7 October 2020
46. Deputy Steven Matthews asked the Minister for Transport his plans to carry out a study on the relationship between road speed limits and the impact on fuel consumption, journey times, air quality and emissions. [29145/20]
Amharc ar fhreagraIn line with our Programme for Government commitment, work is now beginning on new Climate Action Plan. We need to ensure that the new Plan will be ambitious in reach, grounded in evidence, and backed with a determination to achieve Ireland’s emissions commitments in fair and effective ways.
As part of this work, my Department will examine the issue of decreasing speed limits as a potential emission-saving measure, building on previous consideration of the relationship between speed limits and fuel consumption, journey times, air quality and greenhouse gas emissions. The Deputy may recall that the Department explored the impact of reducing maximum speed limits on motorways from 120km/h to 110km/h for cars and vans and from 90km/h to 80km/h for heavy goods vehicles as a potential mitigation measure in the National Mitigation Plan. Further analysis carried out to develop the Climate Action Plan 2019 suggested that such speed limit reductions could abate approximately 1,700kt CO2 of transport emissions between 2020 and 2030.
It is worth noting that the actual reduction in fuel consumption that can be realised through the setting and enforcement of lower speed limits for motorway driving depends not just on the limit, but also on a number of external factors including vehicle types, driving patterns, the frequency of speeding, road load patterns, and congestion levels. I also understand that carbon savings from lower speed can vary markedly for individual vehicles depending on engine characteristics, vehicle weight, distances travelled, and supplementary equipment such as trailers, rear-mounted storage racks or even taxi signs. Over time, the emissions standards for vehicles and the fuels that power them are becoming more stringent, and the use of renewable biofuels as a share of road transport energy has increased significantly over recent years with estimates that, in 2018, biofuel use saved over 500 tkCO2 , over 4% of transport emissions. Such welcome developments will, however, erode the potential emissions reduction benefits of reducing speed limits.
Variable and reduced speed limits have been introduced in other jurisdictions in Europe where, in many cases, the primary focus of such interventions is air quality. For example, in Austria when air quality levels along motorways are poor, speed limits are automatically reduced to 100kph from 130kph.
Transport Infrastructure Ireland (TII) will soon be conducting the enhancing Motorway Operations Services (eMOS) project which will see the introduction of variable speed limits along the M50. The primary aim of this will be to improve the operational efficiency of the motorway by smoothing traffic flow, improving journey time reliability and reducing the number of traffic collisions. It is expected that there will also be environmental benefits arising from the variable speed limiting project.
