The design of a city’s roads is essential to ambitions of reducing emissions, improving traffic flow and increasing safety, according to Juan Carlos Castillo, ACCIONA Roads and Bridges Executive Tech. Leader.
Castillo spoke at the World Road Congress in Abu Dhabi last week, presenting his conclusions from a first of its kind study on the reduction of vehicle emissions on the road through consistent design.
An efficient design results in the reduction of fuel consumption of vehicles, which can be quantified by the emission of CO2 and other contaminating gases. The study is based on a project currently underway by Acciona in Norway.
“The study tries to set up the relationship between vehicles’ emissions and geometry (especially for the horizontal alignment) through its influence in drivers’ behavior,” says Castillo. “The idea is that road itself could suggest the user the speed he should drive within a reasonable range in order to homogenize the traffic flow and control consumption and emissions.”
“All developed countries, especially the GCC and the UAE in particular, as one of the basic pillars of the world’s transportation system, have to take care of the increase in vehicles circulating on the roads and their impact on the environment and population welfare, especially due to the huge growth of its road traffic in the last few years,” he says.
Q and A with Castillo
What were the primary findings of the study?
The main conclusion is that Roads Design should be guided by efficiency criteria and geometry can help for this purpose. Choosing a design speed for the alignment slightly over the posted speed will provide benefits not only in safety but also in a general reduction of fuel consumption and gases emissions, contributing in this way to a sustainable growth of private transport sector.
For this purpose, different horizontal geometries have been tested to compare the variations on consumption of an average vehicle circulating along the alignment of the E-6 RANHEIM-VÆRNES Project, in Norway, and more specifically along the Være-Stavsjøfjell section, a long stretch between two tunnels considered as an isolated section. Using the consumption formula from Dra.
Fonseca from Universidad Politecnica de Madrid and a standard software to simulate the performance of a vehicle type in a free-flow traffic along the different alternatives of geometry, the study shows how a wide horizontal geometry encourage some users to drive much faster as it provides the opportunity of accelerate to a higher speed with no significant difference on their workload.
Thus, consumption and gases emissions would be higher as well as peaks of vehicles’ consumption are higher and more frequent the higher the curvature of the alignment is. On the other hand the geometry with reduced maximum radii and consistent alignment helps to reduce consumption peaks and drive average speed to a figure closer to the design speed for or the vehicles circulating along the road, that means that it is calming the average flow.
Considering ADT 20.000 vh/d in 25 years, differences between the optimal consistent alignment and a nother alignment with wider curvatures has been estimated in savings of more than 11,2 M L of fuel or 20.000 Tn of CO2 emissions.
How will this impact road logistics in Dubai?
The simple application of Consistency design criteria, that can be included into the National Standards, could add the efficiency factor into Roads design, construction and operation placing UAE at the forefront of future road development.
Anyway, using consistency into the Design process and reducing the gap between consecutive curves and the difference of the specific speed of all the curves (which means their radii) to a value closer to the general design speed of the road, will add not only safety for the future customers, but also a reduction on gases emissions from the vehicles circulating.
These criteria can be easily measured and evaluated as a key performance indicator of the alignment during the design process, establishing a previous objective of CO2 total emissions reduction to be achieved for the definitive solution. This reduction can be calculated in the way proposed in the study as a first approach of the sustainability of the road.
Given the rise of e-commerce (more frequent, low volume deliveries) how can this help reduce emissions?
Design criteria with the objective of a more homogeneous flow traffic would involve a better connectivity and effectiveness in short and long trips and potentially a reduction in delivery time. Calming the general traffic flow could improve as well the performance of the low volume deliveries in the same way than the rest of the vehicles.
On the other hand, journeys would be more predictable into an homogeneous traffic, so it would be possible to make delivery timings sure and avoid any potential issue along the way. In summary, effectiveness could be significantly improved into the environment of a traffic flow without unexpected situations.