However, mixed-use development also comes with some challenges for urban design, that require careful planning and management. One of the challenges is how to balance the different needs and preferences of the various users of the mixed-use spaces, such as residents, workers, shoppers, and visitors. For example, some users may prefer more privacy, quietness, and security, while others may seek more openness, liveliness, and accessibility. Another challenge is how to manage the impacts of mixed-use development on the existing traffic and infrastructure systems, such as roads, parking, public transport, water, and energy. For instance, some mixed-use developments may generate more traffic and congestion, or require more infrastructure capacity and maintenance, than the previous land uses. A third challenge is how to ensure the quality and affordability of the mixed-use spaces, especially for the residential units. For example, some mixed-use developments may have lower standards of design, construction, and maintenance, or higher prices and rents, than the market demand or the regulatory requirements.