1 Introduction
2 Review methodology
2.1 Search and selection process
2.2 Scope and terminology
3 A conceptual model of barrier effects of transport infrastructure
4 What are the determinants of the barrier effects of transport infrastructure?
4.1 Transport features
Properties | Type | Description |
---|---|---|
Physical | ||
Static | Motorways and feeder roads, railways, waterways | Fences, railings, noise screens, height differences (embankment, ditches), road width, traffic isles, visual conditions at crossing points [22] |
Dynamic | Transversal, across a feature (car or tram traffic) | |
Longitudinal, along a feature (car or tram traffic) | ||
Psychological | ||
Characteristics of transport features and their environment that have a deterring effect without creating a physical barrier | Conditions for fear of accidents | |
Conditions for fear of crime | ||
Conditions for discomfort | ||
Formal | ||
Traffic rules | ||
Planned infrastructure projects |
4.2 Crossing facilities and routes
Properties | Description |
---|---|
Crossing facilities | |
Number of crossing points | |
Height differences | |
Integration in the local street network | Connection to routes or central mobility strips [131] |
Visual conditions | |
Conditions for fear of crime | Lighting, visibility, escape opportunities, social surveillance [6, 142]. For a further description, see section “Transport features” |
Quality | |
Formal regulation | Pedestrian crossings, traffic lights and possibility to manually control these [87] |
Crossing routes | |
Number of crossing routes | Utilitarian and recreational routes for slow mobility that cross the transport feature [40] |
Connectivity of the street network | Mesh width [40] |
Density of the street network | Network length per hectare or km2 [67] |
Attractivity |
4.3 People’s abilities
Factor | Description |
---|---|
Age | |
Mobility restrictions | Physical and psychological capabilities [67] |
Pregnancy [67] | |
Carrying luggage/shopping [67] | |
Mode of transport | |
Limited or no access to a car | Role in the household [67] |
Financial restrictions [130] | |
Knowledge restrictions | Awareness of transport options [130] |
4.4 Land use
Aspect | Description |
---|---|
Distribution | |
Density | |
Quality | Differences in the quality of service or products offered on both sides of a barrier [26] |
Temporal availability | |
Substitutability |
4.5 People’s needs
Factors | Description |
---|---|
Age | Averages of daily trips, e.g. to playgrounds, bus stops, services for different age groups, can be derived from travel surveys [48] |
Socio-economic | |
Social connectedness within the neighbourhood |
5 What are the barrier effects of transport infrastructure?
5.1 Direct barrier effects
Effects on | Description |
---|---|
Crossing effort | Delays, physical effort, discomfort, stress, and fear of traffic accidents while crossing a transport feature, due to its static or dynamic barrier characteristics or the quality, design or planning of crossing routes and facilities (transversal barriers, see section “Transport features”) [6]*,[18], [29], [71]*,[76]* |
Passing effort | Physical effort, comfort, stress and traffic risks while passing along a traffic feature, affecting cyclists especially (longitudinal barriers, see section “Transport features”). [67, 87, 104] |
Fear of crime | Fear and anxiety about becoming the victim of crime, typically related to crossing facilities [6]* |
Trip effort | |
Change of possibilities for drivers to access destinations located adjacent to a road [17], when the road is upgraded to motorway standard, possibilities to park at the roadside are removed and the number of exits are reduced | |
Travel time between different parts of a farm [20] | |
Accessibility | |
5.2 Indirect barrier effects
Effects on | Description |
---|---|
Frequency of visits | |
Visited destinations | |
Routing of trips | Routing of trips can be changed to avoid barriers [40] |
Organisation of trips | |
Mode of transport |
5.3 Wider barrier effects
6 Which tools have been developed for assessing barrier effects of transport infrastructure?
6.1 Indicators of direct barrier effects
Effect on | Indicator | Description | Technique | |||
---|---|---|---|---|---|---|
Video observation and traffic counting | Site audits | Surveys and interviews | Geospatial analysis | |||
Crossing effort (static characteristics) | Localisation of transport infrastructure | X | ||||
Road width | X | X | ||||
Number of lanes | X | X | ||||
Hindrances along infrastructure | X | X | ||||
Width of central reservation | X | X | ||||
Visual conditions at crossing facility | X | X | ||||
Height differences | X | X | ||||
Crossing effort (dynamic characteristics) | Speed | X | ||||
Volume | X | |||||
Vehicle composition | X | |||||
Direction of traffic | X | X | ||||
Distribution of acceptance gaps | X | X | ||||
Parked vehicles | X | |||||
Risk of traffic accidents while crossing | Number of traffic accidents on a given stretch or point [99] | X | ||||
Crossing effort (facilities) | Distance to a crossing facility | Distance between a street connection with the barrier and the nearest crossing facility [99] | X | |||
Delay at crossing facility | Waiting time for the next opening of a railway or road crossing facility or next ferry crossing. Possibility to control traffic lights manually [40] | X | X | X | ||
Effort required for use of crossing facilities | Height difference to be overcome at bridges over and tunnels under the transport feature [67] | X | ||||
Protection from weather conditions at the crossing facility | X | |||||
Passing effort | Volume | X | ||||
Vehicles composition | X | |||||
Frequency of overtaking | X | |||||
Speed | X | |||||
Fear of crime | Social surveillance | Presence of "social eyes" from entrances, windows, passers-by and surveillance cameras [142] | X | |||
Escape options | Number of alternatives for exiting the crossing facility [142] | X | ||||
Visual conditions | Level of lighting in and around the crossing facility and area around the transport feature. Possibilities for an overview [142] | X | ||||
Trip effort | ||||||
Distance between crossing facilities | X | |||||
Distribution of crossing facilities | Number of crossing facilities per km along the barrier [40] | X | ||||
Number of barriers along routes | X | |||||
Number of disconnected streets | Number of streets that are not connected due to the presence of a railway station and railway [120] | X | ||||
Detour factor | X | |||||
Closeness | X | |||||
Betweenness | Frequency of street segments being part of paths with least impedance between one street segment and all other street segments [42] | X | ||||
Isodistance | Ratio of area reachable with a given street network distance and area within the same distance measured as straight line [67] | X | ||||
Proximity to destinations | X | |||||
Travel time for service vehicles | X | |||||
Accessibility | Catchment areas for facilities | X | ||||
Choice/substitutability of destinations | X | |||||
Accessibility to employment | X | |||||
Degree of separation | “Physical severance index” [35]. Distribution of built area (in sq.m.) and distribution of destinations on both sides of a barrier, expressed as index values. The barrier effect is highest when the built areas and destinations are equally divided on both sides, as this implies the highest level of communications that can be affected. When the built-up area and activities are on one side only, the barrier effect is lowest [35] | X | ||||
Lost population-interaction potential | Number of potential meetings between residents from different neighbourhoods at a common facility that are affected by a barrier [3] | X | ||||
Land use connectivity | X | |||||
Access from roads | Number of exits from a road and travel time for drivers to reach destinations directly adjacent to the road [17] | X |
6.2 Indicators of indirect barrier effects
Effect on | Indicator | Description |
---|---|---|
Frequency of visits | Ratio of changes in number of visits | |
Suppressed pedestrian trips | Number of trips missing in travel behaviour statistics, relative to averages for comparable places. Missing trips can be assumed to be suppressed or that a different mode was chosen [134] | |
Visited destinations | Ratio of changes in destination of trips | Percentage of interviewees indicating that they changed the range of destinations they visit [108] |
Routing of trips | Crossing ratio | “[N]umber of pedestrians who cross a road as a proportion of the pedestrian flow, over a given section or at a specific point” [122]. Registration through video observation |
Ratio of changed routes | ||
Organisation of trips | Ratio of changes in timing and organisation of trips | Percentage of interviewees indicating that they changed their trip timing and organisation [68] |
Mode of transport | Modal share |
6.3 Assessment of wider effects
6.4 Monetisation
Technique | Examples | References |
---|---|---|
Estimated values | Using general estimates to assign a monetary value to a barrier effect | |
Contingent valuation method (measuring Willingness To Pay (WTP) for non-market goods using bidding techniques) | Measuring WTP for avoiding a motorway | |
Measuring WTP for avoiding a barrier to a recreation area | Grudemo et al. [56] | |
Choice modelling (measuring preferences or WTP based on choice experiments involving different combinations of characteristics of a barrier) | Measuring WTP for reducing barrier effects of different types of roads, involving characteristics related to road design, traffic intensity and crossing facilities | Anciaes and Jones [10] |
Measuring WTP for reducing barrier effects of roads | Anciaes et al. [6] | |
Measuring WTP for removing a barrier between two neighbourhoods, taking into consideration amenity characteristics | Grisolía et al. [54] | |
Measuring Willingness To Accept a new road that reduces access to a recreational area, using increased leisure time as a result of decreased travel time as a payment vehicle | Ivehammar [72] | |
Hedonic modelling (measuring WTP for different attributes of housing (e.g. view, distance to station) based on analysis of house sales) | The impacts on WTP for housing related to reductions in accessibility caused by a motorway | |
Objective valuations (using the value of related market goods as proxy for the cost of barrier effects) | Socio-economic costs (increase in traffic accidents, travel time, school transport, sick leave, parking costs etc.) when potential bicycle links are not realised due to barriers | Sælensminde [124] |
Time spent accompanying children to school | Tate and Mara [129] | |
Monetisation of delay | ||
Multiplying the total population by the number of seconds of delay that roads and motorways imply. The resulting time is multiplied by a monetary value | van Essen et al. [139] | |
Demand for crossing facilities as a decreasing function of the generalised cost of crossing (such as time to reach the crossing facility, effort of crossing) | Héran [67] |