april 000001 - Illuminating Engineering Society

. . . . . . . . . . . . . . . . . . . . . . . . . . . D . E S . I G . N . T . R . E N . D . S . . . . . . . . . . . . . . . . . . . . . . . . . . .FIGURE 2. Some of the lighting elements that make up the roadwayvisibility system.per hour is constant and independentof technology designed toimprove safety. However, if perceivedrisk is poorly correlated withactual risk, accidents may increaseand/or traffic flow may bereduced.[5] Thus, the fundamentalgoal for engineering is not toimprove visibility per se, but ratherto increase the correlation betweenactual and perceived risk. If perceivedrisk is closer to actual risk,then driver behavior will be moreimaginary inventions function, roadwayvisibility uses many elements toreach the final goal of providinginformation to the user. In fact, oneissue that has prevented a systemsapproach to roadway visibility in thepast is this focus on individual elements.Answers to visibility issueshave been typically product drivenand not solution driven.Specific roadway visibility elementsinclude: fixed roadway lightingfixtures, roadway markings andIf perceived risk is closer to actual risk,then driver behavior will be moreappropriate for the situation and the goalsof greater safety and increased trafficflow will have been metappropriate for the situation and thegoals of greater safety and increasedtraffic flow will have been met. Thereal goal, therefore, is to engineer theinformation provided, not to justenhance visibility.Components. A large variety oflighting, signaling, signage andmarking elements are available toprovide visual information to the driver.Just as Rube Goldberg usedmany components to make hissigns (traffic signals, traffic and informationalsigns, roadway markers,lane delineators, crosswalks), andvehicle lighting (headlamps, brakelights, taillights, interior displays,back-up lights, fog lights and turnindictors). Figure 2 illustrates someof these elements. Figure 2 also illustrateshow many elements there canbe and how visually noisy the scenecan become.Aside from possibly having toomany lighting and visibility components,these elements can also conflictwith each other. Currently, eachelement is typically designed andspecified in relative isolation to eachother. For example, the IlluminatingEngineering Society of NorthAmerica (IESNA) recommends lightingpractices for roadway lightingwithout taking into account vehicleforward lighting. Similarly, theSociety of Automotive Engineers(SAE) develops standards for automotiveforward lighting without consideringfixed roadway lighting.These two systems obviously interactwith each other. This interactionhas the potential to create redundancyor even worse, to decrease visibility.[6]Stakeholders. There are a largevariety of stakeholders in the roadwaysystem concerned with manyissues, ranging from safety to securityto economic development.[7] Thisraises an important issue. Anychange in the way roadway visibilityis approached will result in the perceptionof some stakeholders beingwinners and some being losers.Since, of course, nobody wants tolose (or be perceived as having lost),proposed changes in thinking canfall victim to inertia. Nobody is. . . . . . . . . . . . . . . . . . . February . . . . . 2004 . . . LD+A . . . 30 . . . www.iesna.org. . . . . . . . . . . . . . . . . . . . . . . . . . . . .