Speed perception by drivers as dependent on target travel speeds, on - - PDF document

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Speed perception by drivers as dependent on urban street design

Victoria Gitelman Fany Pesahov Roby Carmel Transportation Research Institute Technion – Israel Institute of Technology, Haifa, Israel 32nd ICTCT Conference in Warsaw, Poland - October 24 & 25, 2019

Background: Speed in Sustainable road safety

Speed ∼ one of the main issues in Sustainable road

safety and in Safe System

Speed management ∼ matching road infrastructure to

target travel speeds, on every road type

Each road type ∼ a clearly defined function that is

reflected in road design

Need to identify the design features related to speed

selection by the drivers and to apply them in road design to "explain" the target speeds

• In Israel, the guidelines for setting speeds: a new

hierarchy of the road types, with target and design speeds

• A need for design tools to help in implementing the new

approach - matching road infrastructure characteristics to the target speeds Speed choice of a driver ∼ personal characteristics, experience, attitudes and objective factors: environment, road and traffic conditions Road design characteristics affect travel speeds chosen by drivers ↔ Travel speeds are suitable to serve as an objective measure of drivers' perception of road conditions

Previous research

On urban roads, road characteristics ∼ with lower travel speeds*:

• lower posted speed limits, higher density of signalized intersections
• narrow roadways or traffic lanes
• traffic calming measures
• pedestrian activity on the street
• presence of parking lanes
• presence of bicycle or bus lanes
• reduced forward visibility
• side visual narrowing or the proximity of buildings

* Fitzpatrick et al. (2005), York et al. (2007), Edquist et al. (2009), Ivan et al. (2009), Charlton et al. (2010), Bassani et al. (2014)

The study topic

% of vehicles over the speed limit, on urban roads Aim: to examine the relationship between road design characteristics and speeds, on urban roads in Israel Focus on collector streets, with 50 km/h speed limits:

• High % of traveling above the speed limit (national surveys)
• Mixed land uses, significant vehicle traffic volumes and high

pedestrian activities >>> road safety problems, particularly, pedestrian accidents (1) Field surveys - to collect data on road characteristics, travel speeds, vehicle and pedestrian volumes; Examination of relationships between actual travel speeds and other street characteristics (2) A driver survey - attitudes towards appropriate speeds on various street sections; Examination of road and driver characteristics related to “perception” of appropriate speeds

• How urban road characteristics are perceived by drivers - reflected in

actual travel speeds and in choosing the speeds "appropriate", according to drivers' opinions, to each road section

Methodology: Field surveys - data collection and analyses

• Collector streets: in city centers and on

boundaries of residential areas ∼ in 15 medium- and large-sized cities

• 5 types of road layout
• Field surveys: in working days, 10am-1pm
• Units: street sections of ∼ 200 m in length
• Road characteristics (categories): lane width,

visual narrowing, commercial frontage, visibility distance, parking configuration, presence of bus stops, presence of pedestrian crosswalks, types of intersections

• Speed measurements: 30 free-flow vehicles
• Counting vehicles, walking and crossing

pedestrians: in 5 min (twice) >>> hourly estimates Multivariate regression models (stepwise) single-lane dual- carriageway multi-lane dual- carriageway two-way single- carriageway two-lane one-way

• ne-lane one-way

1 2 3 4 5

Methodology: Drivers’ opinion survey

At 10 sites (various cities), 20 drivers per site, each driver – opinion on 4 street sections (800 responses). Cities ∼ the composition of socio-economic clusters in drivers’ population Questionnaire:

• Background information: age group, gender, driving experience, acquaintance with the area…
• A set of safety-related statements ∼ the manner of travel in the city
• Visual presentation of street layouts ∼ to judge the speed limit and appropriate travel

speed A stock of street pictures: 15 representative layouts (using 4 major types and lane width, parking type, visual narrowing…); for each site - 4 sets of 4 pictures Multivariate analyses: a relationship between the driver and street characteristics and “appropriate” speeds (stepwise) Face-to-face interviews, in proximity to the areas of field surveys: near gas stations and open shopping malls On working days, between 10-17

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Results: Field surveys

Layout type N of sites Hourly vehicle traffic Hourly no of walking pedestrians % crossed at crosswalks % crossed not at crosswalks Mean speed, km/h 85- percentile speed, km/h % over speed limit 5) Multi-lane dual- crw 30 1279 555 9 14 44 51 22% 4) Single-lane dual-crw 9 659 539 15 23 36 43 5% 3) Single-crw 19 724 449 7 25 34 40 5% 2) 2-lane one-way 10 729 496 5 18 35 41 1% 1) 1-lane one-way 12 442 491 2 21 32 37 1%

• Data on 80 street sections: traffic volumes ∼ different by road layout types; hourly

average of 450-550 walking pedestrians

• Multi-lane dual-carriageway streets ∼ highest vehicle volumes and highest speeds
• On all street types, pedestrians crossed not at the arranged crosswalks (14%-25%)
• Mean and 85-percentile speeds ≤ 50 km/h but on all street types were vehicles

travelling over the speed limit

• Correlation between speed indicators >>> mean speed values for modelling

Results: Field surveys - models for actual travel speeds

Variables Model A Model B B Sig. B Sig. Constant 41.13 0.00 41.07 0.00 Layout type (1-5) 2.90 0.00 2.42 0.00 Hourly no of pedestrians

• 1.32

0.00

• 1.25

0.00 Presence of pedestrian attractions

• 3.27

0.00

• 3.68

0.00 Hourly vehicle traffic 0.84 0.01 0.82 0.01 Types of intersections#

• 1.30

0.05

• 1.46

0.03 Variables Model C B Sig. Constant 52.93 0.00 Median’s (un)transparency 3.16 0.00 Presence of pedestrian attractions

• 3.68

0.01 Presence of visual narrowing

• 2.82

0.03 No of pedestrians who crossed not at the crosswalks

• 0.69

0.01 (non)Presence of bus stops

• 3.07

0.03 Model a: 4 layout types and 3 exposure variables. Model b: 5 layout types and 4 exposure variables. Model c: without layout and volumes.

#1- all signalized, 2- mixed, 3- all un-signalized

• Models A-B ∼ close. Actual travel speeds ∼ influenced by the road layout, higher on streets

with higher vehicle volumes; lower on streets with higher pedestrian activity, higher presence of commercial frontage and with un-signalized intersections at their ends

• Model C: actual travel speeds decrease with higher presence of visual narrowing on the street

and when more pedestrians cross the street not at the marked crosswalks

• Higher speeds ∼ on sections with more visual intrusions on the median and with presence of

bus stops >>> moderators of the road layout

Results: Drivers’ opinion survey*

Speed limits and appropriate speeds, km/h, as reported by drivers (N=200) Layout Speed limit Appropriate speed mean sd mean sd A Single-lane dual-crw 47.1 7.3 42.0 10.6 B Multi-lane dual-crw 50.9 7.8 48.9 10.3 C Single-crw 46.9 8.8 42.3 11.4 D One-way 45.2 8.3 39.6 10.7 significant difference, p<0.01 *36% response rate Multi-lane dual-carriageway Speed limit Appropriate speed Single-carriageway Speed limit Appropriate speed

km/h km/h

Results: Drivers’ opinion survey (2)

• Cluster analysis: homogeneous groups of drivers acc. to their responses to safety statements

Average values of agreement* with statements (sd), by group Group (n) In city center I always drive at speed below 50 km/h On street with many crossing pedestrians I slow down On street with many parked vehicles I slow down On street with signalized junctions I speed up On street with many travel lanes I speed up 1 (104) 4.7 (0.5) 4.9 (0.3) 4.5 (0.7) 2.7 (1.1) 4.1 (0.6) 2 (50) 4.5 (0.8) 5.0 (0.2) 4.8 (0.4) 1.4 (0.6) 1.9 (0.8) 3 (46) 2.5 (0.8) 4.4 (0.9) 3.6 (1.0) 2.5 (0.9) 3.8 (0.8) *scale 1-5, from “fully disagree” to “fully agree” Intermediate Most careful Tend to higher speeds Layout Group Appropriate speed – mean, km/h Dual-crw single- lane 1 42 2 40 3 45 Dual-crw multi-lane 1 48 2 44 3 54 Single-crw 1 42 2 40 3 46

Results: Drivers’ survey - models for “appropriate” speeds

All models: layout type affects the selection of appropriate speed Low visual narrowing, cities with a higher socio-economic level >>> higher speeds Driver lives/works in the area, belongs to groups with safer attitudes >>> lower speed Higher speed limit (reported) >>> higher appropriate speeds

Variables Model 1 Model 2 B Sig. B Sig. Constant 42.0 0.00 36.9 0.00 Layout A (1,dual-crw) 2.2 0.03 2.2 0.04 Layout B (m,dual-crw) 8.0 0.00 8.0 0.00 Layout C (single-crw) 1.6 0.15 1.6 0.15 Socio-economic cluster 1.2 0.00 1.7 0.00 gender

• 3.2

0.00

• 3.2

0.00 Visual narrowing (1-low) 1.9 0.04 1.9 0.04 drivers' group 2

• 6.3

0.00

• drivers' group 1
• 3.9

0.00

• Variables

Model 3 B Sig. Constant 14.9 0.00 Layout A 1.2 0.19 Layout B 5.2 0.00 Layout C 1.5 0.09 Speed limit 0.7 0.00 gender

• 3.2

0.00 Driver lives/works in the area

• 1.5

0.02 drivers' group 2

• 5.9

0.00 drivers' group 1

• 3.5

0.00 Model 1: layouts, driver characteristics, groups, road characteristics. Model 2: without driver groups. Model 3: plus speed limit.

Re-fitting of models with actual speeds >>> a direct link to appropriate speeds

Conclusions

A consistency between the actual and “perceived” speeds >>> supporting the possibility to rely on drivers’ perception in road design Road layout - the most influential characteristic for speed selection >>> more constricted street layout (one lane per direction/ one-way) is perceived as moderating speeds and leads to lower actual speeds Measures for lowering travel speeds on collector streets: moderating road layout, higher visual narrowing, increasing the amount of pedestrian attractions For some street layouts, the drivers believed that the appropriate speed should be lower than existing limit (50 km/h) >>> rising awareness of road safety concerns in drivers’ population

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Victoria Gitelman Transportation Research Institute Technion - Israel Institute of Technology, Haifa, Israel trivica@technion.ac.il