Assessing the utilization of pavement shoulders on South Africa’s national roads: a Conjoint approach

Pavement shoulders are critical elements of roadway infrastructure, supporting safety, structural durability, and traffic operations. However, their rapid degradation and misuse, particularly on high-speed national roads, highlight the need for improved design strategies. This study aims to investigate how key pavement shoulder design attributes influence driver behaviour and decision-making. Using Conjoint Analysis, a statistical method for multi-attribute preference evaluation, a survey of 162 motorists in Gauteng Province, South Africa, was conducted to assess preferences across attributes such as shoulder width, surface material, and roadside furniture. Findings reveal that pavement shoulder furniture (50% importance), surface type (33.3%), and width (16.7%) significantly impact drivers' likelihood of proper shoulder use. Wider shoulders without any pavement shoulder furniture were most preferred, while paved or vegetated surfaces and the presence of guardrails were also viewed positively for promoting safer and more predictable usage. The study provides evidence-based recommendations for optimizing shoulder design to enhance road safety, prolong infrastructure lifespan, and support sustainable traffic management. These findings contribute to user-oriented pavement design standards for national highways in high-traffic regions.