Roadway design that maximizes safety for all users is not a simple, black-and-white exercise. With nearly 7,000 pedestrians and over 900 cyclists killed on U.S. roads annually, according to National Highway Traffic Safety Administration (NHTSA) data, the urgent need for safer multimodal design has never been clearer.
The numbers tell a sobering story: Traditional roadway design that prioritizes vehicle throughput over safety for all users is costing lives. A new mindset and approach to developing transportation infrastructure is needed. It will require flexibility, thoughtful planning and a commitment to safety for everyone who uses roads — not just motorists but also cyclists, pedestrians and other vulnerable road users (VRUs).
How Multimodal Infrastructure Impacts Safety
How communities connect and move people is important and differs depending on transportation objectives and needs. Intentional design can create safe spaces for all road users. Understanding what modes of transportation are used in an area can help inform design decisions, such as the type of shoulders on a highway, the width of sidewalks for pedestrians or whether buffers should further separate traffic from adjacent properties. Predictive modeling software is often used to consider various design features based on safety concerns.
When designing transportation infrastructure, engineers face a fundamental challenge: balancing the needs of various users within limited space and with limited resources. Every second of signal time given to pedestrians is time taken away from vehicles. For every lane converted to protected bike infrastructure, that capacity is removed from motor vehicle traffic.
Successful transportation design balances immediate community needs with sustainable growth patterns while taking into account immediate and long-term economic feasibility. Additionally, designers must account for rapidly evolving mobility patterns and see to it that their solutions integrate existing infrastructure and potential future transportation paradigms. Five factors to consider include:
- Safety requirements for all users. Who is being served and what are the safety implications? Identify the primary users and their specific needs. Every design decision must prioritize reducing conflicts between different modes and minimizing the risk of crashes, especially for vulnerable users who lack physical protection.
- Traffic flow and capacity demands. What are immediate and projected traffic demands? Engineers must consider how many vehicles need to move through a corridor efficiently to avoid creating gridlock that impacts emergency response times, transit operations and economic vitality.
- Surrounding environment. What are the immediate and nearby areas like? Urban, suburban and rural settings each demand different solutions. An area’s character, density and land use patterns fundamentally shape appropriate and effective design solutions.
- Long-term maintenance considerations. How will ongoing upkeep be handled? Seemingly effective and efficient design fails if maintenance responsibilities aren’t clearly established and carried out. For example, debris accumulation in bike lanes or traffic signal equipment failures can quickly render transportation systems unusable or unsafe.
- Community priorities and needs. What is the community vision now and for the future? Solutions must align with broader transportation and land use goals, as well as with the values and preferences of residents and stakeholders, including accessibility requirements, economic development goals and quality-of-life considerations.
Understanding Separation Options
There’s a spectrum of options for separating different road users, each with varying levels of protection and interaction. The greater the speed and volume of motor vehicle traffic, the more robust the separation typically needs to be. Selecting the appropriate level of separation involves weighing factors like available right-of-way, anticipated user types, adjacent land uses and implementation costs. A few separation options include:
- Cycle tracks. Cycle tracks provide dedicated lanes for bicyclists with physical separation from both vehicular traffic and pedestrians. These protected bike lanes typically feature vertical elements like curbs that create a safer environment for cyclists while enhancing visibility to motorists at intersections.
- Sidepaths. These multiuse facilities accommodate pedestrians and cyclists on the same path, positioned alongside each other but physically separated from the roadway. Sidepaths offer positive protection through elements like curbs and buffers, creating a safer experience for nonmotorized users.
- Trails. As distinct pathways apart from roadways, trails provide complete separation from motor vehicles. Trails offer maximum safety for pedestrians and cyclists but may not always be practical for transportation corridors.
Safety Enhancements Beyond Separation
Physical separation isn’t the only tool available to designers. Strategic operational improvements can significantly enhance safety. In fact, many of the most dangerous interactions occur at intersections and conflict points where separated facilities must reconnect with the broader transportation network. Thoughtful signal timing, pavement markings and technological solutions can help manage critical transition areas where different modes of transportation interact. Among these solutions are:
- Leading pedestrian intervals (LPIs). Interactions among vehicle drivers, bike operators and pedestrians vary, with pedestrians often requiring more time at signals. Balancing signal time is crucial, as it aims to provide adequate time for walkers while not excessively disrupting traffic flow. Implementing LPIs gives pedestrians and cyclists a head start at intersections before vehicles receive a green signal. This simple timing adjustment increases the visibility of vulnerable users and reduces conflict with turning vehicles, often with minimal impact on overall traffic flow.
- Signal coordination for nonmotorized users. Advanced detection systems can identify cyclists approaching intersections and adjust signal timing accordingly. Visual indicators can then communicate to cyclists when it’s safe to proceed, creating a more coordinated system for all users.
Context Sensitive Design
Perhaps the most crucial concept in modern transportation design is context sensitivity. This approach recognizes that a single solution cannot be universally applied across all environments. Context sensitive design acknowledges that roads pass through varyious environments, from dense urban cores to suburban neighborhoods to rural landscapes — and that design solutions must be tailored accordingly.
Case in point: In a bustling downtown with high pedestrian activity, physical separation between transportation modes may be essential. However, in a suburban area with moderate activity, marked bicycle lanes might be sufficient. Conversely, extended shared-use paths could adequately serve cyclists and pedestrians in rural settings with lower density.
Whether in a small neighborhood or a large business corridor, it is vital to understand how to manage transportation growth effectively, which often occurs quickly. When it comes to transportation planning, analytic tools such as origin-destination studies, traffic demand modeling and land use predictive analysis play a significant role in understanding what future growth could look like and how transportation should be used to help safely manage that growth.
Real-World Applications
Several of our successful projects demonstrate how safety design principles can be applied. From urban corridors with integrated multimodal systems to rural highway redesigns that dramatically reduced accident rates, our portfolio showcases solutions prioritizing human-centered design and operational efficiency:
- The Eighth Street Project implemented vertically separated bike and pedestrian infrastructure with coordinated signals that detect cyclists and provide visual indicators for safe passage.
- The Mission Road Project added bike lanes to improve cyclist safety without disrupting traffic flow.
- Mercy Way Corridor Improvements Project improved safety, flood control and aesthetics through various design enhancements.
- The Farmington Creekside Trail Project created a fully separated path for recreational and transportation use with raised refuge islands, a new rectangular rapid flashing beacon crosswalk and improved lighting.
- The Vulnerable Road User Corridor Safety Assessment Project evaluated existing infrastructure and offered recommendations for context-appropriate improvements.
Making Safe Transportation Design Decisions
The most effective designs result from collaborative processes that engage community stakeholders throughout the planning and implementation phases. Ultimately, transportation designers must consider several key factors when determining the appropriate design approach. These include safety, environmental impact, accessibility for diverse populations, long-term maintenance costs and adaptability to future technological innovations.
The future of transportation design isn’t about choosing cars over bikes or pedestrians — it’s about finding the right balance for each mode of transportation while prioritizing safety for all. Designing transportation infrastructure that serves all users is undoubtedly more complex than the vehicle-centric approaches of the past. However, with thoughtful application of context-sensitive design principles, appropriate separation techniques and strategic transportation system improvements, engineers can create safer, more accommodating roads for everyone.
