| 1. |
- Charoenwong, C., et al.
(författare)
-
The effect of rolling stock characteristics on differential railway track settlement : An engineering-economic model
- 2022
-
Ingår i: Transportation Geotechnics. - : Elsevier Ltd. - 2214-3912. ; 37
-
Tidskriftsartikel (refereegranskat)abstract
- Railway track geometry deteriorates under repeated train loading. When linespeed is increased or new rolling-stock is introduced this can alter the future rate of change of differential settlement and track geometry. Therefore this paper presents a novel combined engineering-economic approach to investigate the effect of increasing train speeds, adding additional passenger movements, and adding additional freight movements to an existing line. Firstly a numerical algorithm is presented to compute differential track settlement. An important novelty of the model is its use of the wavenumber finite element method coupled with settlement relationships in a manner that allows for track irregularities to evolve after every load passage (i.e. taking into account the evolution of the track unevenness profile before applying each subsequent train passage). Unlike traditional approaches this allows the model to faithfully simulate mixed traffic conditions, including the coupled interactions between different rolling stock types and track geometry. The engineering model is used to predict tamping intervals, and then coupled with an economic model capable of calculating deterioration elasticities and marginal costs. It is shown that higher speeds result in higher dynamic forces and cause a faster rate of deterioration of track geometry, thus increasing marginal cost. The model is then used to investigate the effect of adding additional train movements to a passenger line. It is shown that additional movements increase the rate of track degradation and marginal costs, particularly if the additional traffic is freight. This is because freight vehicles typically have one only layer of (stiff) suspension, thus generating elevated dynamic forces compared to passenger vehicles. © 2022
|
|
| 2. |
- Yarmuchamedov, Sherzod, 1983-, et al.
(författare)
-
Competitive tendering, ownership and cost efficiency in road maintenance services in Sweden : A panel data analysis
- 2020
-
Ingår i: Transportation Research Part A. - : Elsevier Ltd. - 0965-8564 .- 1879-2375. ; 136, s. 194-204
-
Tidskriftsartikel (refereegranskat)abstract
- This paper uses econometric methods to study the cost efficiency of road maintenance provision in Sweden for the first time. The novelty lies in the application of econometric techniques to a new and rich panel dataset (73 contracts; 11 years, 2004–2014) with a wide range of variables and approaches to controlling for heterogeneity (including weather variation). The analysis is applied in the context of a sector where all road maintenance contracts are subject to competitive tendering, but with a state-run provider competing against private firms. The key focus is whether, even after competitive tendering, efficiency differences remain between the state provider and private entrants. We find that the state-run provider has significantly higher costs (between 8 and 20%) than private firms despite holding 60% of the market. The results suggest that substantial savings are possible through opening up road maintenance to the private sector through competition for the market; but that in Sweden, the tendering process is still not working optimally. Further research is needed to understand why the current cost gap persists between public and private providers, despite competitive tendering having been present across the whole market for several years. © 2020
|
|
