Here we describe the most basic category of situational measures - those designed to increase the difficulties of crime - beginning with target hardening. Situational prevention is sometimes dismissed as being nothing more than this, though it is only one of the 25 techniques that the approach encompasses. Note that there is considerable overlap between the techniques. For example, target hardening makes crime more difficult, but it can also slow up offenders and increase their chances of getting caught. Some measures can also serve more than one purpose. When using this classification, do not spend time worrying where a particular measure fits use it only to ensure that you consider the widest possible repertoire of situational responses to a particular problem.

Harden targets. An obvious, often highly effective way to obstruct the vandal or the thief is through physical barriers such as locks, screens, or reinforced materials. The introduction more than 30 years ago of steering locks in this country and overseas brought about long-term reductions in car theft, and ignition immobilizers are now reinforcing these benefits. Anti-robbery screens in London post offices have reduced robberies by 40 percent and bullet-resistant passenger screens have cost-effectively reduced assaults and robberies committed against cab drivers in New York City (see Robbery of Taxi Drivers, Problem-Oriented Guides for Police No. 27, accessible at www.cops.usdoj.gov and www.popcenter.org).

Control access to facilities. Keeping people out of places they have no right to be, such as military camps, factories, and apartment blocks, has a long pedigree think only of the portcullises, moats, and drawbridges of medieval castles. It is also a central component of Oscar Newman's concept of defensible space, arguably the start of scientific interest in situational prevention. Barry Poyner has demonstrated that the installation of entry phones and the demolition of walkways linking buildings significantly reduced muggings at a London estate (Step 24). In some cases, access controls are intended to ensure the possession of tickets and documents. The redesign of tickets to make them easier to check produced a sharp reduction in fare evasion on Vancouver, Canada ferries. In the most famous example, baggage and passenger screening at airports in the early 1970s contributed to a reduction in the number of airline hijackings worldwide from about 70 to 15 per year.

Screen exits. The purpose of exit screening is to ensure that those leaving a building, a facility, or some other place have not stolen anything or have paid all fees and taxes. Passengers on the Washington, D.C. subway must insert their tickets in the automatic gates not only when entering the subway, but also on leaving. This provides two opportunities to check that the fare has been paid. On the New York City subway, passengers must insert their tickets in the gates only once, when entering the subway, thus reducing the chances of detecting fare evasion. Other examples of exit screening include border controls on leaving a country and the use of electronic tags in library books and merchandise. These tags activate an alarm if books have not been checked out or if a thief tries to remove a tagged item from the store. Studies have shown that they significantly reduce shoplifting and theft of library books.

Deflect offenders. Rival groups of soccer fans in the U.K. are segregated in the stadium to reduce fighting, and their arrival and departure is scheduled to avoid the waiting periods that promote trouble. Scheduling the last bus to leave immediately after pub closing time is intended to interfere with another of Britain's less admirable traditions, the closing time brawl. These are examples of deflecting offenders away from crime targets, a situational technique suggested by routine activity theory. Other examples are provided by road closure schemes that have produced reductions in many kinds of crime (see Closing Streets and Alleys to Reduce Crime, Problem-Oriented Guides for Police, Response Guide No.2, accessible at www.cops.usdoj.gov and www.popcenter.org). Even drive-by shootings in Los Angeles have been reduced by street closures (see box).

Control tools and weapons. Saloons in the Wild West routinely required customers to surrender their pistols on entry because of the risk of drunken gunfights. More recently, so-called "safer" handguns have been developed that can only be fired by the owner or which shoot wax bullets or tranquilizers. To prevent glasses being used as weapons when broken, many pubs in the U.K. now use "toughened" beer glasses. The first commercial use of Caller-ID (in New Jersey at the end of the 1980s) produced a 25 percent reduction in obscene telephone calls. Step 34 lists the different ways in which cities have attempted to control the use of public phones in drug dealing, including blocks on incoming calls and banning them from specific locations. Re-programming of public phones at the Manhattan bus terminal prevented illegal access to international phone service, thus wiping out a multi-million dollar scam perpetrated by hustlers. Improved security procedures for delivering credit cards produced a substantial drop in credit card frauds in this country in the mid-1990s (Step 11).

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