Enhancing E-Scooter Safety with Acoustic Vehicle Alerting System (AVAS)

Introduction

E-scooters have rapidly become a popular mode of transport in urban areas worldwide. However, their silent operation poses significant safety challenges, particularly for pedestrians and other vulnerable road users (VRUs). To address this issue, TIER Mobility, in collaboration with UCL PEARL and Anderson Acoustics, embarked on a project to develop a Universal E-Scooter Acoustic Vehicle Alerting System (AVAS). This case study explores the project’s objectives, methodology, key findings, and recommendations.

Who is UCL PEARL? 

Our partner on this project was the University College London Person-Environment-Activity Research Laboratory that is a state-of-the-art customisable laboratory space where the lighting, sound, smell and physical features can all be controlled to study the brain and senses. This facility and the expert research team led by Nick Tyler enabled the project team to test a range of sound profiles in controlled conditions to understand how pedestrians hear and react, prior to the on-street testing. 

Project Objectives

The primary aim of the project was to create an AVAS that could be safely detected and localised in various urban environments while promoting a positive public perception of e-scooters. The objectives included:

• Developing a universal AVAS sound based on urban environmental context and stakeholder needs.
• Implementing the sound on e-scooters using integrated hardware.
• Ensuring the sound is favourable in terms of safety and subjective likeability.
• Testing with key stakeholders in laboratory and on-street to validate performance. 

Methodology

The project followed a collaborative approach involving TIER Mobility, UCL PEARL, and Anderson Acoustics. The methodology included:

• Baseline research to identify sound opportunity areas and performance metrics.
• Lab-based experiments by UCL PEARL to test various sound options.
• Support on developing an AVAS specification and integration of the sound in a prototype hardware solution. 
• Development of an on-street soundscape survey to understand and gather perceptions of various AVAS options.
• On-street experiments to validate the sound options in real-world scenarios with key stakeholders, including people representing vision impairment and other disabilities (the Independent Disability Advisory Group (IDAG).  

Key Findings

Research and Lab Tests

• The research highlighted the need for a sound with at least two layers: a continuous background sound and a main impulsive element.
• UCL PEARL’s lab tests identified three shortlisted sound options (Sounds 2, 3, and 4) for system implementation and on-street testing.

System Integration

• Anderson Acoustics developed a customized AVAS specification and system logic for integration into the TIER IoT system, that increased pitch with increasing speed. This involved coordination between the TIER system engineers, bench testing and prototype implementation for on-street testing.

On-Street Tests

• On-street experiments were conducted in two locations: Exhibition Road (quiet environment) and Park Lane (busy environment).
• The tests found that the sound levels on the E-scooter AVAS options were not always sufficient to be noticed by pedestrians. This is expected to be due to limitations of the speaker weatherproof casing and how it restricted sound propagation and directionality.
• Among the sound options tested, Sound 4 was considered the most suitable due to its richness and specific pitch, making it more easily detected.

Final Sound Selection

• Sound 4 was the final preferred AVAS option, with the majority of participants choosing it. It was found to be the most effective in helping listeners understand the operational behaviour of the e-scooters, such as speed and acceleration/deceleration.

Further Recommendations

• Further refinement of the E-scooter AVAS sound and integration system prior to full roll-out.
• Involving stakeholders with cognitive and physiological impairments in future trials.
• Developing a technical specification that includes optimal performance metrics.
• Conducting quality checks and maintenance before deploying the final AVAS on operating fleets.

Conclusion

The development of a Universal E-Scooter AVAS by TIER Mobility, UCL PEARL, and Anderson Acoustics represents a significant step towards enhancing e-scooter safety in urban environments. The project’s collaborative approach, rigorous testing, and stakeholder engagement have resulted in a sound that effectively alerts pedestrians and improves public perception of e-scooters. With further refinements and broader stakeholder involvement, the AVAS can be successfully implemented to ensure safer and more inclusive urban mobility.