Mixed use

A mixed use development consists of a building or group of related buildings (e.g. a scheme) which are used for more than one purpose, such as a series of retail units at ground floor level, office units at first floor level and residential apartments on upper levels.

Description

A mixed use object supports by definition various uses. On one hand, this makes making generic statements about this kind of object very difficult, as various combinations of use have very different characteristics. On the other hand, the mixed structure of this object is the main feature that distinguishes it from the other types of urban objects and this feature has some specific considerations.

The fact that various functions are combined into one object type, means that these functions interact and this can lead to effects not present in uniform types of urban objects. It will be these effects we will focus on on this page.

Function

Social

Mixed land use can enhance the vitality and perceived security of areas by increasing the number of people on the street and in public spaces at different times of the day. Mixed use development also encourages more efficient use of land and can lead to a more equitable city design, allowing for reduced travel and associated costs for residents.

Mixed use settings particularly demonstrate the high relevance of societal security as a frame of reference for identification of vulnerability and enhancement of resilience - for example, social/community vulnerability in view of the growing number of threats from global terrorism, natural disasters or crime. Urban planning practice must therefore incorporate appropriate security measures for vulnerability identification and resilience enhancements of urban objects, including from the societal point of view. Vulnerability assessment of urban objects in particular in mixed-use settings should thus take place based on different sets of indicators, from physical to social, and across several levels of reference, from individual to cultural community.

It is important to consider that a society is not confined to the semiotics of architectural structure in perceiving and interpreting the vulnerability of its material environment as well as social and economic structure. Since design cannot alter human nature, it cannot be a direct answer to crime and insecurity. However, design can reduce insecurity and increase security by addressing the underlying causes, as well as the types of behaviour that lead to insecurity, such as crime. This behaviour has cultural roots that need to be understood and included in vulnerability assessment.

Such an assessment can be done based on:

• List of indicators for assessment of subjective protection requirements of critical infrastructure
• Types of impact of critical infrastucture failure on citizens and society and needs to protect it
• Societal aspects of failure of critical services

Aspects like those listed above show how important it is to involve citizens in related urban-object risk assessment. VITRUV identified a set of practical methods for such citizen participation.

Economic

The primary function of a mixed use development is in the provision of a mix of varied but compatible land uses such as residential housing, retail and services, offices and appropriate industrial activities. The main goal of these kind of dwellings is to develop a high quality urban environment in terms of jobs, income, real estate value and societal value. Mixed use developments yield economic benefits in terms of the optimum use of infrastructure (less need for car use due to the small distances), increasing social interaction, and thus a richer, more vibrant urban life. On the other hand, it involves higher risks for developers since all elements of the mixed use development need to be successful. Like any urban development, mixed use development creates economic effects for the local and regional economy. This occurs both in terms of spatial development (temporarily) and the economic activities that are taking place in these areas (permanent activities). The economic impact of offices can be estimated with the help of economic tools/techniques.

The location of mixed use development can raise specific security issues due to the mix of residential housing, retail, public services, offices and infrastructure. On the one hand, mixed use dwellings are benefiting from more social interaction during the day and week, reducing the risk of crime types such as burglary, robbery, graffiti, etc. On the other hand, as mentioned above, there is a higher risk of underutilisation of the mixed use development than single use dwellings due to a lack of interest in certain elements of the mixed use dwelling (e.g. office space and/or residential units) which could result in partly abandoned dwellings, making an urban object more vulnerable for types of crime that are prone to lack of surveillance and low levels of security (such as burglary and vehicle theft). On top of that, more crowded places are also more vulnerable for crime types like pickpocketing and vandalism. In all cases, crime generates costs in anticipation of crime (e.g. locks, surveillance, etc.), as a consequence of crime (loss of property) and in response to crime (police investigation, legal system, etc.). Indirectly, crime has (amongst others) an impact on, for example, the local real estate value.

Apart from the more traditional security measures such as policing, alarm systems, surveillance and regulatory bodies, the ‘designing out’ or 'sustainable design' approach in the earliest stages in the planning process can be in the long run an effective measure from an economic point of view to prevent security threats and to reduce the economic damage.

Mobility

From the mobility perspective, mixed use zones are efficient in the sense that travelling distances between different types of destinations (work, leisure, living) are short. A relatively large part of the trips are made by pedestrians and cyclists (also called vulnerable road users) and public transport.

Safety

An important aspect of mixed use development is that safety requirements from one use can extend into areas used differently. For example, the safety requirements for a transportation hub include specific requirements that normally do not apply (to the same extent) to residential areas. However, when developing an object with a mixed use of both transportation hub and residential area, one should be careful to prevent threats associated with one use to affect another use, not designed to deal with the threat. Another example would be an industrial area which also serves as a node for road traffic. Although the industrial design would normally suffice to avoid excessive risks due to industrial incidents, the presence of a busy road can aggravate the impact to a degree that would require measures that would not be necessary if used either as transport node or industrial area.

Security Issues

A mixed use development can also raise specific security issues. Analogous to the safety issues arising when uses are combined, the presence of for example a use that would be attractive for attack by fanatics with a use that would attract crowds, can lead to a security sensitive situation that far exceeds either situation apart.

A mixed use area can also benefit from multiple uses, as the weakness from one use can sometimes be relieved be a second use and vice-versa. This principle is for example used in mixed commercial and residential areas, where the shops ensure a sufficient population in the street in the daytime and the residential use ensures a natural surveillance during the night time. This can potentially reduce the risk of crime types such as burglary, robbery, graffiti, etc.

There are no security issue that are specifically associated with mixed use. Rather, one should be weary of amplifying effects of security issues present from one use by another use.

Measures

There are no measures specifically suited to counteract the effects of mixed use of an area. Basically, the measures valid fro each of the uses still apply. The only way to avoid unwanted amplifying effects of security issues by mixed use is to be aware of them and to attune the design and the measures to these effects and minimise (or negate) them.