Accessibility is an important determinant of regional and local development (Clark 1958). Transport infrastructure and services expand the opportunities for households to access distant jobs and amenities, and support, inter alia, the emergence of agglomeration benefits for firms. Hence, accessible places and regions have long attracted economic activity (Axhausen 2008: 5).

After a phase of relative decline, passenger rail transport has experienced a resurgence as a transport mode in Europe during recent decades. Several societal and technological developments have contributed to this reinvigoration. Tertiarisation and the rise of the knowledge economy have increased demand for face-to-face communication and business travel (Hall/Pain 2006: 7; Thierstein/Lüthi/Kruse et al. 2008). This has supported reurbanisation and a tendency towards polycentric development which involves the major metropolitan cores (Münter/Volgmann 2014) being increasingly organised in a global space of flows (Castells 1996). These processes are advantageous to passenger rail as a linear, mass-transport oriented form of transport, which furthermore often directly services inner-city areas and allows travel time to be used for work purposes. At the same time, rail infrastructure can reinforce this pattern towards “integrated corridor economies” (Blum/Haynes/Karlsson 1997: 1). Changing consumer preferences with regard to ecological concerns are also an advantage for rail as opposed to air and road travel due to its relatively low emissions (cf. Schwarzer/Treber 2013). Finally, there have been technological and managerial improvements, particularly in the form of high-speed rail which has greatly increased average speeds on some routes. This has improved the competitive advantage of passenger rail for many routes. Hence, passenger rail accessibility plays a growing role in locational decisions.

However, accessibility is unequally distributed in space, and the described developments have sometimes contributed to a widening of rail accessibility disparities between regions. Particularly, the introduction of high-speed rail has been discussed in scientific literature as promoting a polarisation of accessibility between metropolitan cores on the one hand and peripheral areas on the other, on a European scale and also within several European countries (Spiekermann/Wegener 1996). Its capital intensity and technical characteristics mean that high-speed rail is established first on routes between major metropolitan centres, while parallel, slower conventional services with more frequent stops are in some cases discontinued. At the same time, conversely, it has been argued that high-speed rail can serve cohesion goals when it links peripheral and central regions (Monzon/Lopez/Ortega 2019: 527). Likewise, recent decades have seen an increased profit orientation and the (partial) privatisation of several national rail providers throughout Europe with adverse consequences for regional accessibility in some countries, as peripheral and tangential lines often have the lowest internal profitability. On the other hand, progressing European integration has in some cases reduced the peripherality of border regions in the rail network.

Despite numerous (mostly ex-ante) studies in several European countries and for Europe as a whole, there have been few assessments of the development of rail accessibility in the case of Germany. During the last three decades, the rail network has been influenced by the triple effects of reunification, the de jure privatisation of the railway service provider, and the construction of more than 1,000 km of new high-speed rail infrastructure, which has reshuffled regional accessibility. Accessibility studies in countries with a monocentric urban structure and radial network development, such as France, Spain and the UK, have often found accessibility changes to be essentially a function of the reduction of travel time to the main metropolis. The polycentric spatial structure and dispersed network layout in Germany means that accessibility developments are expected to be less clear.

Furthermore, continuing digitalisation of previously analogous data means that new sources become available for use in research, such as historical timetables that allow an ex-post assessment of accessibility levels. The research presented by this paper exploits a novel source, a digitalised database of German long-distance rail timetables from 1987 until today.

The aim of the paper is to analyse and visualise the spatially differentiated development of rail accessibility among German regions during the last 30 years. We develop a monomodal rail accessibility model for 266 functional city-regions in Germany in 10-year intervals between 1990, the year prior to the introduction of high-speed rail in Germany, and 2020, using potential accessibility and degree centrality indicators. Our study links back to the considerable body of research on regional accessibility changes caused by European integration published during the 1990s, and re-examines their ex-ante projections and results against the background of longitudinal and current data gathered using novel methods and sources. The main research question is: Has the spatial distribution of passenger rail accessibility in Germany become more equitable during this time period?

The paper is structured as follows. In the subsequent second section, we briefly revisit previous rail accessibility analyses in Europe before we provide more detail of our case study in Section 3. The fourth section describes the methods and data used. In the fifth section, we present results before concluding with more general remarks and implications in the sixth section.

Rail accessibility changes can be analysed on different spatial scales, from the station surroundings to the regional (Mohino/Loukaitou-Sideris/Urena 2014) and national scales. This paper is focused on the regional scale, as we are interested in the effects of inter-regional infrastructure and service changes, even though accessibility changes on the local level can be substantial as well, particularly in the case of line closures, which merits a separate discussion. We hence conceptualise these regions as ‘containers’ which are uniformly affected by an accessibility change.

There is a rich literature on regional accessibility (including rail) on a European scale, starting with Keeble, Owens and Thompson (1982). ESPON (2015: 46–55) offers a comprehensive overview. Many of these studies date back to the 1990s, where the first phase of high-speed rail construction and the fall of the iron curtain triggered an initial wave of research, and are static. As it was still too early to measure accessibility effects, many of these studies are now outdated, or only present forecasts but no evaluation.

Regarding the general distribution of rail accessibility, most studies confirm the well-established ‘blue banana’ (Brunet 1989) pattern of an arch of high population density in north-western Europe with the highest accessibility of population (e.g. Poelman/Ackermans 2016). Results for multimodal accessibility similarly often find Paris and Frankfurt to be the centres of accessibility in Europe for longer trips, and for continental and global accessibility (BAK Basel Economics 2007: 16). Martín and Reggiani (2007: 558) estimate dynamics of rail accessibility and describe a shift in the centre of gravity within the EU from Paris eastwards in the decade between 2007 and 2020. Peripheral regions on the Iberian Peninsula are often identified as being least accessible by rail. However, there are also situations we call ‘inner peripheries’ and ‘outer cores’: some (mostly rural) regions that are geographically central within Europe are much less accessible than the agglomerations (Spiekermann/Neubauer 2002: 26). On the other hand, agglomerations, typically the capitals, in countries that are geographically peripheral within Europe can nevertheless exhibit a high level of rail accessibility (Lutter/Pütz/Spangenberg 1993). Compared to road, rail accessibility is much more concentrated and discontinuous, but infrastructure investments can have a stronger influence on the distribution (Spiekermann/Wegener 2006: 16).

The dynamics of rail accessibility have been studied particularly under the lenses of European integration and high-speed rail development. High-speed rail is commonly defined as newly built lines for speeds of 250 km/h or more, and upgraded lines for at least 200 km/h (European Council 1996); speeds in Europe reach 320 km/h. First developed in Japan with the Shinkansen in 1964, high-speed rail has been introduced in and between a number of European countries, including Italy (1977), France (1981), Germany (1991) and Spain (1992). International high-speed rail corridors within the EU only materialised at a late stage, mainly as part of the Trans-European Networks (TEN) programme, and essentially involved stitching together the national networks (Vickerman 1997: 22). Network length and ridership have since grown strongly

http://www.uic.org/spip.php?action=telecharger&arg=102 (15.12.2020).

High-speed rail networks were essentially developed nationally by the (state-owned) railway companies and vary e.g. with respect to network structure, intermodality and station placement, which can all have a decisive influence on accessibility outcomes. Monocentric and politically centralised countries typically exhibit a network structure more radially aligned to their capitals (cf. Albalate/Bel/Fageda 2012). Systems range from fully segregated separate high-speed rail infrastructure to full integration between conventional, high-speed rail and even freight traffic (Campos/de Rus 2009). Integrated systems are typically more expensive, but allow a better trickling-down of accessibility effects. There are also differences regarding station placement and service provision. While the capital intensity and technical characteristics of high-speed rail typically mean that it is first implemented between major centres over the shortest possible distance, some lines include (out-of-town) stations in peripheral and rural areas that happen to be located on such axes, greatly increasing their accessibility. On the other hand, there is the risk of a reduction of accessibility, particularly for smaller regional centres, if conventional rail services are discontinued after the opening of parallel high-speed rail lines (Bruinsma/Rietveld 1993: 934; Vickerman 1997: 26).

Spain now has the longest high-speed rail network in the world after China, both of which have attracted substantial academic interest (e.g. Cao/Liu/Wang et al. 2013; Monzon/Lopez/Ortega 2019; Ribalaygua/Perez-Del-Caño 2019). The scientific debate on the question of whether high-speed rail increases or decreases accessibility disparities between regions has been inconclusive. On the one hand, several studies associate high-speed rail with an increasing ‘polarisation’ of accessibility and hence economic discrepancies or at least new layers of advantages and disadvantages on a European (Spiekermann/Wegener 1996: 38) and national scale (Plassard 1994: 61). High construction and running costs mean that high-speed rail is usually first implemented between the most populous and economically dynamic regions, improving their connections and mutual accessibility, but not that of the area in between (‘tunnel effect’). Such an increasing disparity is not necessarily accompanied by lower absolute accessibility levels in remote regions. Transport infrastructure and services in remote regions can be unchanged, or even slightly improved and their absolute accessibility levels increased, but in relative terms their accessibility decreases compared to the central regions where accessibility gains are even higher (Schliebe 1983; Spiekermann/Wegener 1996); Hall (2009: 65) called this the “peripheralization of the periphery”.

On the other hand, several authors highlight the balancing effect of high-speed rail. Using average travel times to a number of chief economic activity centres weighted by GDP, Gutiérrez, González and Gómez (1996) find that the greatest increases in relative accessibility within the EU can be registered in regions in which (foreseeably) the stations of the future network will be located, but the greatest accessibility increases in absolute terms correspond to the peripheral regions. They highlight that high-speed rail also has an important symbolic dimension for cohesion. Lutter and Pütz (1993) assume strong changes of regional attractiveness through high-speed rail, particularly for peripheral regions with an existing economic base, and plead for a European transport policy that seeks homogenous infrastructure provision across regions. Several more recent studies on a national level have likewise found beneficial effects of high-speed rail for the evenness of accessibility (Gutierrez 2001; Monzon/Lopez/Ortega 2019). Nevertheless, the economic effects even of an accessibility increase for peripheral regions are contested, a “straw effect” could mean that they lose economic activity to the core regions (Ottaviano 2008: 19). In any case, such effects are context-specific and far from automatic (Chen/Hall 2011). Many authors highlight that for high-speed rail to reduce regional disparities, mixed-mode services combining high-speed and conventional stretches and intermodality at high-speed rail stations are important for spreading accessibility benefits to a wider area (Vickerman 1997: 32; Martínez Sánchez-Mateos/Givoni 2012; Chen/Hall 2013).

The review shows that there is a need for more analyses on the dynamics of accessibility disparities. Many of the recent studies specifically treat a selected single line, while systematic studies across cases are rare. Several authors call for greater attention to be paid to comparative, quantitative accessibility analyses over a longer time frame (Levinson/Wu 2020: 149) and between different states of networks (Axhausen 2008: 20; BBSR 2019: 103), and demand continuous accessibility modelling (Stępniak/Rosik 2018: 309).

The development of railway infrastructure and services in Germany has been characterised by three broad trends during recent decades: high-speed rail construction, privatisation and the aftermath of German reunification.

The construction of several new high-speed rail lines in West Germany started in the 1970s, after a long phase of little investment in rail infrastructure. The conventional rail network in Germany was considered outmoded and unfit fur purpose (Schliebe 1983), also because the traditionally strong east-west routes were severed. Construction followed a demand-driven rationale, mostly in north-south orientation, as despite the strong growth of car and lorry traffic some lines were operating at their capacity limit (Schliebe/Würdemann 1990: 227-229). In contrast to other European countries, the new lines were designed for freight train use as well, to connect the southern industrial regions with the harbours in the north. This required gentler slopes and hence expensive tunnelling and bridging in the hilly terrain of central Germany, which significantly increased costs and landscape encroachment (Jänsch 1991: 367). Planners also aimed for interoperability between conventional and high-speed rail, i.e. high-speed trains also use conventional lines, and conventional intercity trains and even regional trains use stretches of the high-speed network, a “fully mixed” network mode (Campos/de Rus 2009: 20-21). After the opening of the first high-speed rail line in Germany between Hannover and Würzburg in 1991, the ‘Inter-City Express’ (ICE) brand was introduced for high-speed trains. The ICE soon reached the expected passenger volumes and profitability (Jänsch 1991). To date, seven high-speed rail lines covering 1260 km have been completed.

The privatisation of railways has had an effect on rail services in recent decades throughout Europe. The UK went furthest with the full privatisation of rail operations in 1994, including the network infrastructure. Other European countries re-organised and sometimes semi-privatised their mostly still national rail companies, initiated by EU legislation on equal access to infrastructure networks and a reform of the subsidy regime for transport provision. In general, many of the still national, integrated companies were separated into a network and a service operation company, and often further subdivided into freight and passenger rail. The German state railway company Deutsche Bundesbahn was transformed into a private enterprise (Deutsche Bahn, DB) in 1994, but with 100 % of the shares in public ownership. Successive governments aimed for a (part-)divestment, but the plan was ultimately dropped in the 2008 financial crisis. Together with EU laws on public transport subsidies, the reorganisation meant the concentration of DB on profitable long-distance lines, while (inter)regional services were discontinued or left to be subsidised and competitively tendered by the federal states.

A special circumstance in the German case is the reunification of its eastern and western parts in 1990. Many connections across the inner-German border, particularly local lines, had been severed since the establishment of the two German states and were subsequently re-established in the years after 1990. The two separate railway companies were merged. In addition, a set of large-scale transport infrastructure projects, the “German Unification Transport Projects” (Verkehrsprojekte Deutsche Einheit, VDE) were set up to reconnect east and west and improve transport infrastructure in East Germany. They included nine rail projects, among them two new high-speed rail lines, at an investment volume of approximately 15 bn euros (Holzhauser/Steinbach 2000: 129).

Recently, there have been calls for Deutsche Bahn to refocus on its role as a domestic supply-oriented public service provider, rather than a profit-oriented internationally operating firm, particularly to be able to implement climate protection targets. Following the example of the Netherlands and Switzerland, rail policy is also increasingly oriented towards optimising seamless interchanges and adapting infrastructure to the desired ‘integrated timetable’, rather than vice versa. The most recent Federal Transport Infrastructure Plan (Bundesverkehrswegeplan) with a time horizon of 2030 allocates about 40 % of new investment in transport infrastructure to rail projects and contains eight new passenger high-speed lines for 250 km/h or more, including those necessary for integrated timetables, the so-called Deutschland-Takt (BMVI 2016: 41).

Also see https://www.bmvi.de/SharedDocs/DE/Artikel/E/zukunftsbuendnis-schiene.html (15.12.2020).

There have been few studies specifically on regional rail accessibility in Germany. Evangelinos, Hesse and Püschel (2011) calculated a combined rail accessibility indicator for Germany consisting of gravitational accessibility of economic output, daily accessibility of population within four hours and relative network efficiency. The research found that Frankfurt by far dominates the ranking, before Düsseldorf, Hannover and Köln; Trier being last. Regarding accessibility dynamics, Steinbach and Zumkeller (1992) projected that high-speed rail expansion would lead to the creation of a continuous zone of equally high rail accessibility throughout south-west Germany. Schliebe and Würdemann (1990: 233) estimated an average rail travel time reduction between German regions of 45 minutes between 1990 and 2000. Using a contour-based travel time model without distance decay, they estimated that a high number of region pairs would fall within the critical four-hour threshold for daily return business trips. Beneficiaries were particularly the (then capital) city of Bonn, and the West in general, while they were pessimistic for Berlin. This study did not take into account the VDE projects. Holzhauser and Steinbach (2000) closed this gap and simulated the accessibility effects of the post-reunification transport projects, concluding that the economic cores of eastern Germany (particularly Saxony, Saxony-Anhalt and Thuringia) would profit most, thereby balancing accessibility across the country’s regions. In addition, they highlighted that Berlin would be released from its peripheral position.

The aim of the empirical part of this paper is to estimate rail accessibility for business trips in Germany on a regional scale between 1990, the year before the opening of the first high-speed rail line, and today. Despite their often positive and significant relationships, “macro-level models” (Berechman 1995: 22), which use some measure of the capital stock (e.g. km of road) as an explanatory variable, fail to account for the fact that transport infrastructure investments are not made in isolation. The alignment and position in the network of such investments provide a vital context for their effects (Banister/Berechman 2001: 210; Axhausen/Fröhlich/Tschopp 2006: 3). Accessibility measures, which consider the actual services provided by infrastructure networks, are thus preferable.

Accessibility can be defined as the “potential for opportunities of interaction” (Hansen 1959: 73) of a territory or place and can be measured in various ways. Detailed overviews of the operationalisation of accessibility can be found in Song (1996), Geurs and van Wee (2004) and Levinson and Wu (2020). In this paper, we mainly use two accessibility measures: potential accessibility using an exponential decay function, and degree centrality. Each specific accessibility indicator captures only some dimensions of the accessibility concept; hence, it is useful to combine several sub-indicators (Martín/Reggiani 2007: 555). Potential accessibility shows the advantages that a rail connection provides in terms of proximate contact partners within a typical daily return travel journey, while degree centrality emphasises direct connectedness without changeovers, with no distance decay.

This section describes our findings. It is structured as follows. First, we show the distribution of accessibility by region separately for the different points in time 1990, 2000, 2010 and 2020, respectively. Next, we visualise the changes of accessibility during this period. Finally, we present results on the question of whether the changes amount to an increase or decrease in regional accessibility disparities.

This paper has reviewed previous studies of regional rail accessibility in Germany and complemented them by an analysis of changes in rail accessibility of 266 functional urban areas in Germany for four points in time: 1990, after German reunification and before the introduction of high-speed rail, 2000, 2010 and 2020. The study used a potential accessibility measure based on an exponential decay function calibrated for business trips, and a degree centrality measure for direct regional connections. The analysis confirms the general pattern of accessibility distribution with regions in the ‘blue banana’ of Europe exhibiting the highest accessibility levels. Regarding the dynamics, we find no evidence for growing rail accessibility disparities in Germany, despite the discontinuation of intermediate long-distance trains and the construction of high-speed rail infrastructure. Instead, there has been an accessibility increase across all regions throughout the study period. High-speed rail has led to extraordinary accessibility improvements in some cases, but the refurbishment of conventional rail lines and reopening of formerly dismantled cross-border lines in eastern Germany after 1990 have largely overshadowed the effects of high-speed rail, particularly in the first decade after reunification. Regarding degree centrality, we find a reduction of direct change-free connections between regions in favour of a concentration of long-distance lines on major metropolitan hubs.

High-speed rail effects in Germany have furthermore transcended the classical urban-periphery dichotomy and are spatially more extensive, but also more discretionary than in other European countries. This is due to the interlinkage of high-speed and conventional rail, the more dispersed settlement structure and piecemeal implementation of high-speed rail. Unlike in other countries, the most accessible region is not the capital city. We find a cohesive development of rail accessibility during the study period, which can however mostly be attributed to the first decade, 1990-2000, and has since come to a halt. Since then, both population development and the alignment of new high-speed rail lines have strengthened the accessibility of southern German regions.

The chosen approach has limitations. Particularly, the results might contrast with the local experience of rail line closures and discontinuation of services in the 1990s and 2000s. However, the study takes regions as spatial base units, which means that local lines within regions are not considered. Further improvements of the analysis should contrast the findings with accessibility for other modes, particularly road and air, also multi- and intermodally, and take generalised costs into account rather than pure time costs. Furthermore, recent studies have used a more time-geographical perspective and have highlighted the critical importance of certain time thresholds with regard to high-speed rail business trips (e.g. Chen/Hall 2011; Moyano/Rivas/Coronado 2019). This perspective could be fruitful for further research regarding the German public transport system, as it is not yet considered widely in interregional transport. The analysis of betweenness centrality would likewise reveal changes in the importance of certain regions as hubs.

This paper has concentrated on travel times between regions as the main determinant of accessibility. For an integrated and seamless transport system, which is the policy goal of the current Federal Transport Infrastructure Plan and its “Deutschland-Takt”, well-timed interchanges are more important than speed alone. Instead, ‘sufficient’ travel times between interchange nodes should guide infrastructure investment. A refinement of the methodology used here could take interchanges into account more explicitly.

Finally, it is interesting to reconsider that two of the first high-speed rail lines (Hannover-Würzburg, 1991; Berlin-Wolfsburg, 1998) were planned and partially constructed before German reunification, in a way that bypassed or transited East Germany. Transport infrastructure is costly, changes slowly and potentially has long-lasting implications on flows of people, goods and services. The accessibility maps shown in this paper would likely look different had reunification occurred earlier, pointing to the potential role of ‘longue durée’ (Braudel 1958; Wallerstein 1979) processes in regional economics.