Robin Liggett

Synthesis and Optimization of Small Rectangular Floor Plans

This paper describes a set of algorithms for the production of a certain class of architectural plans. Each plan is made up from rectangular rooms arranged within a simple rectangular overall plan shape. The effective upper limit on the number of component rectangles which may presently be treated is eight. Given certain specified requirements as to which rooms shall be adjacent, the algorithms produce exhaustively all topologically distinct arrangements of rooms in which those requirements are satisfied. Constraints on the dimensions and areas of each room may then be introduced. Several approaches for the dimensioning of the rectangular arrangements have been explored. In certain cases, appropriate dimensions may be found by solving simultaneous linear equations. Under special conditions linear programming may be used to find that assignment of dimensions to rooms which gives least cost—where cost is for example calculated as a function of the enclosing surfaces. A more general solution may be found with the use of nonlinear programming methods. One further possibility, where dimensions are allowed to vary only by modular increments, is for all feasible dimensional solutions to be enumerated exhaustively.

Death on the Crosswalk: A Study of Pedestrian-Automobile Collisions in Los Angeles

This research explores the spatial distribution of pedestrian-automobile collisions in Los Angeles and analyzes the social and physical factors that affect the risk of getting involved in such collisions. More specifically, this study investigates the influence of socio-demographic, land use, density, urban form, and traffic characteristics on pedestrian collision rates. We first provide an exploratory spatial and statistical analysis of pedestrian collision data in the city of Los Angeles to identify preliminary relationships between the frequency of collisions and socio-demographic and land use characteristics at the census tract level. This aggregate level analysis points to major concentrations of pedestrian collision data which are used at a second stage of the research for more qualitative and detailed analysis of specific case studies of intersections with high frequency of pedestrian collisions.

Optimal space planning in practice

Abstract The Computer Aided Design Groups Space Planning System, a general facility for optimal spatial arrangement of activities in buildings, is described. Case studies of application in practice are presented and discussed, and the influence of practical experience with real spatial arrangement problems on the design of the software is described.

An Integrated Environment for Urban Simulation

This paper presents a strategy for integrating a fully three-dimensional environmental simulation system with an industry-standard computer-aided design system and a traditional two-dimensional geographic information system and databases. The integrated system provides a full package for modeling, exploration, and display of alternative physical environments. The proposed links between the systems are discussed with respect to the efficiency of the simulation process as well as the user interface.

BUS STOP-ENVIRONMENT CONNECTION: DO CHARACTERISTICS OF THE BUILT ENVIRONMENT CORRELATE WITH BUS STOP CRIME?

Can we understand why some bus stops are safe and others are crimeridden? Can we predict which features of the bus stop environment are likely to encourage or discourage crime? Can we design safer bus stops? These questions are addressed by exploring the relationship between environmental variables and bus stop crime. An earlier study used crime data, along with environmental indicators, for a sample of 60 bus stops in downtown Los Angeles. Crime rates were higher for bus stops near alleys, multifamily housing, liquor stores and check-cashing establishments, vacant buildings, and graffiti and litter. In contrast, good visibility of the bus stop from its surroundings and the existence of bus shelters contributed to lower crime rates. This earlier study was indicative but not predictive of the elements that contribute to bus stop crime. With the geographic and temporal expansion of the data (covering a larger city part over a longer time span), a series of regression models was generated that identify environmental predictors of bus stop crime. These models show that the most important predictor of crime is location. If the environment is controlled, undesirable facilities and litter result in higher crime rates, whereas visibility and many pedestrians lead to lower crime rates. The presence or absence of certain characteristics in the bus stop microenvironment can affect crime. Also, the appropriate design and layout of the physical environment can reduce opportunities for criminal actions.

Virtual modeling of urban environments

Researchers at UCLAs Departments of Architecture and Urban Planning are using state-of-the-art visual simulation technology to build virtual worlds that can be used by planners, designers, and community groups to visualize and evaluate proposed changes and new developments in the urban environment. This paper focuses on the modeling methodology that has evolved for efficiently creating three-dimensional (3D) virtual urban worlds. It is illustrated with reference to actual projects that have recently been completed or are currently under development.

JOURNEYS TO CRIME: ASSESSING THE EFFECTS OF A LIGHT RAIL LINE ON CRIME IN THE NEIGHBORHOODS

The implementation of new transit lines is some times dogged by concerns that such lines may increase crime rates in station neighborhoods. Affluent communities have often complained that transit lines transport crime to the suburbs. This study focuses on the Green Line transit system in Los Angeles and examines its effects on crime in the adjacent areas. The Green Line light rail system passes through some high-crime inner city neighborhoods and terminates at its western end in affluent suburban communities. The study examines neighborhood level and municipality-wide crime trends for five years before and five years after the inception of the line. A piecewise regression model is developed to evaluate the impact of the opening of the line in the station neighborhoods. GIS analysis is also utilized to identify spatial shifts in crime hot spots for municipalities abutting the Green Line. At the end, the study establishes that the transit line has not had significant impacts on crime trends or crime dislocation in the station neighborhoods, and has not transported crime from the inner city to the suburbs.

An environment for real-time urban simulation

Drawing from technologies developed for military flight simulation and virtual reality, a system for efficiently modeling and simulating urban environments has been implemented at UCLA. This system combines relatively simple 3-dimensional models (from a traditional CAD standpoint) with aerial photographs and street level video to create a realistic (down to plants, street signs and the graffiti on the walls) model of an urban neighborhood which can then be used for interactive fly and walk-through demonstrations. The Urban Simulator project is more than just the simulation software. It is a methodology which integrates existing systems such as CAD and GIS with visual simulation to facilitate the modeling, display, and evaluation of alternative proposed environments. It can be used to visualize neighborhoods as they currently exist and how they might appear after built intervention occurs. Or, the system can be used to simulate entirely new development.

The Quadratic Assignment Problem: An Analysis of Applications and Solution Strategies

A wide variety of practical problems in design, planning, and management can be formulated as quadratic assignment problems, and this paper discusses this class of problem. Since algorithms for producing optimal solutions to such problems are computationally infeasible for all but small problems of this type, heuristic techniques must usually be employed for the solution of real practical problems. This paper explores and compares a variety of solution techniques found in the literature, considering the trade-offs between computational efficiency and quality of solutions generated. Recommendations are made about the key factors to be considered in developing and applying heuristic solution procedures.

Interactive graphic floor plan layout method

Abstract A new approach to the interactive solution of optimal floor plan layout problems is presented. The method is based upon the use of probability theory to predict the likely consequences of activity location decisions, combined with use of low-resolution raster graphics displays. It not only generates high quality results, but also provides the designer with a structural understanding of the space of alternatives being explored.