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Table 8 Indicators of direct barrier effects

From: Disentangling barrier effects of transport infrastructure: synthesising research for the practice of impact assessment

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 [21, 40, 87]     X
Road width Road width that needs to be crossed in meters [21, 40, 87]   X   X
Number of lanes [21, 40, 87]   X   X
Hindrances along infrastructure Fences, noise screens, etc. [21, 40, 87]   X   X
Width of central reservation [21, 40, 87]   X   X
Visual conditions at crossing facility Lines of sight at the crossing facility [21, 40, 87]   X   X
Height differences Bank on which the transport feature is located or if the feature is placed in a trench [21, 40, 87]   X   X
Crossing effort (dynamic characteristics) Speed km per hour [40, 99, 122] X    
Volume Vehicles per hour [40, 99, 122] X    
Vehicle composition Proportion of heavy vehicles (trucks, busses) in the total traffic flow [40, 99, 122] X    
Direction of traffic Left/right [40, 99, 122]   X   X
Distribution of acceptance gaps Related to the grouping of passing vehicles, measured by adding reaction time, crossing time and a safety margin. It must be considered that different social groups (e.g. age groups) have different reaction times, crossing times and safety margins. [57, 58, 122] X   X  
Parked vehicles Number of parked cars along a street [67, 122]   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 Roofs and screens at bridges for shelter from rain and wind [6, 67, 95]   X   
Passing effort Volume Vehicles per hour [48, 67, 130] X    
Vehicles composition Proportion of heavy vehicles (trucks, busses) in the total traffic flow [48, 67, 130] X    
Frequency of overtaking Number of vehicles that overtake a cyclist [48, 67, 130] X    
Speed km per hour [48, 67, 130] 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 Distance between crossing points; benchmarks: within urban environment max 300-500 m, outside urban environments max 1,000–1,500 m [6, 9, 40, 67]     X
Distribution of crossing facilities Number of crossing facilities per km along the barrier [40]     X
Number of barriers along routes Number of barriers along existing slow mobility routes (utilitarian and recreational) weighted by e.g. attractiveness, presence of signage and its cultural heritage value [40, 64, 67, 132]     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 Ratio of network distance and straight-line distance between given origins and destinations [40, 66, 67]. Benchmarks for average detour ratio: 1,15–1,25 in urban areas, 1,3 in regular grids [67]     X
Closeness Proximity of single street segment to all other street segments within a given travel distance [23, 42]     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 Network distance/travel time/travel cost from each address point to the nearest facility within a given group of facilities. Also, the number of households affected by longer travel distances to a given selection of facilities can be calculated [14, 15, 138]     X
Travel time for service vehicles Travel time for service vehicles such as ambulances, public transport and waste collection [41, 67, 95, 138]     X
Accessibility Catchment areas for facilities Number of residents or households within the catchment area of each facility within a given category of facilities. Catchment areas are measured using network distances and are defined as overlapping or exclusive areas [37, 138]     X
Choice/substitutability of destinations Number of destinations within a given group of destination that are accessible from each address point within a given travel time. The effect of the barrier will be lower if more than one destination is accessible [50, 130, 133, 138]     X
Accessibility to employment Accessibility to job opportunities, measured by number of jobs or revenue of the workplace, inversely weighted by travel time [2, 76]     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 Number of barriers that are crossed by straight lines drawn between neighbourhoods and neighbourhoods or between neighbourhoods and given destinations [2, 40, 46]     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