Adaptation of road infrastructure to climate change

Project 7
Comparison of meteorological parameters at federal highways with raster data of climate projections
Source: Federal Highway Research Institute (BASt)

Description

Anticipated climate change will, during the coming decades, become increasingly evident in the most varied spheres of life. In unfortunate cases, this can lead to load limits for roads or engineering constructions being reached or exceeded. In order to gain better insight, this research project deals with the development of algorithms to enable the application of values taken from regional climate models (climate change projections) to the conditions on road properties or infrastructures. The project is limited to thermal parameters (temperature changes) and precipitation.

The aim of the research is to clarify as to whether load limits of road structures or engineering constructions are exceeded as a result of climate change. This goes along with a nationwide consideration of federal highways.

For the projection of climate data, the dynamic regional model REMO (Regional Model) will be used. REMO quantifies the distribution of various meteorological parameters for the coming decades with a high spatial and temporal resolution.


Methodology

Observational data taken from 62 road ice warning systems and newly installed climate change (KLIWA) weather stations is available for 30 selected hotspots areas that, in the future, will experience considerable climate changes. These Measurement points on federal highways are broadly divided according to their surroundings, as follows:

  • Roads in open locations
  • Roads in woodland
  • Roads with perimeter buildings or perimeter growth
  • Roads on bridges

In addition, information on the road’s pavement material (concrete or asphalt) is available, as well as photos of the routes. Further important thermal component variables to be taken into consideration are location characteristics, including geographical latitude and longitude, ground level and course of the road (East-West orientation or North-South).

The situation on the road is being compared with the conditions at a closely situated DWD station. As the amount of data collected on the roads is often too low to form a solid, statistical hypothesis, a numerical model is used to simulate the data in terms of thermal parameters.
Map of monitored hotspots featuring location characteristics of the road ice warning systems and new KLIWA weather stations

The analysis will be conducted on 62 neighbouring measurement station pairs (federal highways and DWD) for the following meteorological parameters:

  • Number of summer days (T≥25°C)
  • Number of hot days (T≥30°C)
  • Periods with days T≥25°C
  • Periods with days T≥30°C
  • annual maximum temperature
  • Freeze-thaw cycle
  • Precipitation > 10 mm/h or > 20 mm/d.

A linear correlation between road surface temperatures and temperatures at heights of 2 m is assumed and algorithms are determined between DWD stations and pavement temperature of federal highways.

With the help of REMO climate projection data, the regression relation findings (separate for asphalt and concrete carriageways) are used to simulate future thermal conditions and heavy rainfall conditions at the federal highways where the 30 hotspots are located.

The calculated algorithms are independent of applied regional climate projections and therefore can also be used in other climate projection data.


Results

The REMO projected temperature data show maximum values of 74°C up until the end of the century for pavement temperatures in terms of open location, asphalt carriageways at the Passau hotspot location. In comparison, the road surface temperatures in Hannover reach a maximum of 57°C (asphalt). Concrete carriageways are 3 - 4°C colder. Also federal highways surrounded by woodland, on bridges or with perimeter obstructions were around 1.5°C, 1.0°C or 0.3°C cooler than comparative routes in open locations.

All parameters during the cold seasons, such as freeze-thaw cycles or the number of days with frost or ice, showed an almost linear decrease during the 21st century, so that these extreme values are only relevant up until 2035.

In regards of precipitation, two projection periods, 2021 – 2050 and 2071 – 2100, only show minimal changes, where one should also take into the account considerable uncertainties in precipitation calculations.

Based on these projection data and drawn from other literature sources, the research project assessed as to whether road or engineering construction load limits will be exceeded as a result of climate change. It showed that, as a rule, it will predominantly be transport safety (including rutting and potholes) and durability (change in material, fatigue, cracks) that is affected by climate change. In particular asphalt pavements experience permanent malfor-mation and damage due to increased ambient temperatures in summer.

Maximum temperature values will, in the future, mean that certain standards and measurement bases will need to be changed. However, changing boundary condition standards (e.g. year of construction, planned period of use) have to be taken into account in order to prevent uneconomical dimensioning.

One possibility in terms of adapting norms would be the consideration of a climate adaptation factor in dependency of further boundary conditions. Thus, in the case of bridges, timely intervention is already required in contrast to roads, due to their long working life.

Aside from material characteristics, the microclimate also plays a significant role in component temperature, as it does exposure of infrastructure elements. Thus, temperature changes of up to 22°C can occur on construction surfaces, depending on the carriageway materials’ surface reflection properties (light/dark). Concrete roads do not heat up as intensely as as-phalt roads. This effect was confirmed by the temperature data at hand.

For the mathematical dimensioning of asphalt pavements, temperature gradients are overlapped with traffic loads. The traffic requirements will, in the future, increase both in terms of intensity as well as in transport tonnage or axle load. In the future, traffic-induced damages will outweigh climate change related alterations.


Project data

Projektdaten

Term of project: 01/01/2012 – 30/11/2014

Contractor:
Büro für Umweltbewertung und Geoökologie, Gießen
Institute of Meteorology and Climatology, Leibniz Universität Hannover
Institute of Building Materials, Concrete Construction and Fire Protection, TU Braunschweig

Contact:
BASt unit Z5
This email address is being protected from spambots. You need JavaScript enabled to view it.

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