 The traffic control system consists of many types of devices that are commonly defined. Markings and signals, maintenance of the devices is essential to proper performance. During regular inspections, when a need for maintenance is identified, a decision must be made. Is the need a non-critical one that can be accomplished by scheduled routine maintenance or Is it an emergency where the risk to the motoring public is very great and immediate action must be taken? The manual on uniform traffic control devices for streets and highways illustrates the basic marking patterns. For liability reasons, these should always be followed. Markings are the most basic level of communications with the motorist and therefore proper maintenance is critical. Failure of pavement markings to be visible or easily understandable can cause the motorist to make a driving error. Frequent inspection, both by day and by night, is the key to identifying the maintenance needs for the marking system. What looks like perfectly good paint markings by day may be barely visible at night. Inspection should stress reflectivity. Glass beads are what make the paint stripe reflect the headlight beams at night. If they are lost through traffic action or if not enough have been placed on the paint stripe, the paint stripe stops being effective when the sun goes down. Restriping schedules vary with ADT, weather and environmental conditions. Typically, a 36-month period is the maximum that can be expected on a low-volume roadway. The maximum may be as short as three months on high-volume roadways. The painting frequency will be based on agency policy, the need and scheduling of other related construction activities such as overlays. Unneeded stripes must be removed completely. Several methods are in common use to remove paint lines including grinding, sandblasting, hydroblasting and excess oxygen burning. All paint removal methods leave scars that can mislead a motorist. An overlay or seal coat are the only positive treatments for paint line removal. In situations like construction detours where pavement markings are definitely temporary, fabric backed temporary pavement marking tape can be used. The fabric in the tape allows it to be removed without scarring the pavement even after an extended time period. The danger maintenance crew space with any exposure on high-volume freeways combined with a short life of traffic paint justifies the cost of durable marking materials. When water covers paint or plastic stripes, they are not easily seen by the driver. Raised pavement markers stand above the water film and are easier to see. Raised pavement markers, however, are removed by snow plows if they are not especially protected. When placing markers, the epoxy must cover the entire base of the marker with a little excess along each edge. Poor epoxy contact like this results in prematurely lost or damaged markers. The small amount of two-part epoxy needed for marker replacement on an individual basis can be a problem when the two parts come in gallon drums. One solution is to use two grease guns with a single lever to force out equal amounts from each gun. Recently, bituminous adhesives have become popular in several states because of their ability to really stick markers to hot mix. Old Moor trailers can be modified to carry the hand-pushed bituminous adhesive applicator. This one is an experimental prototype. A trailer transforms the applicator into part of a rapid rolling operation. The driver of the tow vehicle positions the guide boom on a paint stripe. Desired marker spacing determines which side guide is used. The driver stops when the side guide reaches the correct place on the stripe. The applicator operator releases some adhesive. Then hand signals for the driver to roll forward until the button placer is over the adhesive and signals for the rig to move on as soon as the button is down. With this arrangement, a rate of about four buttons a minute can be maintained all day. For safety, two shadow trucks, one with an arrow board are used. Delineators and object markers must be properly positioned and maintained in order to be an effective means of communication and not mislead the driver. If the pavement markings are clear and effective, the driver will not have to concentrate so hard on where the road is going that he cannot spare any attention for the signs. Signs are a part of the whole in communicating the driving situation to the driver. There are three major types of signs, regulatory and guide, including informational and directional. A sign must be easy to read under normal conditions. Night is a normal condition so field inspections must include night as well as day reviews. Faded signs such as this one should be scheduled for replacement or refurbishment. Buildups of soot, dirt or other pollutants on the face of the sign should be washed off to make the message readable. A metal sign that is unreadable but otherwise undamaged can be refurbished by stripping it and applying a new sign face. Clean loose material from the sign face. Put a new background of reflective sheeting on it. Care must be taken to prevent warping or bubbling the reflective sheeting. Warped reflective sheeting will reflect the headlights poorly or strangely and may confuse motorists. Large guide signs are more economical to refurbish than small signs. This newly refurbished guide sign should last about 15 years before it needs another facelift. Sign vandalism is a major maintenance problem and cost. Alterations of speed limit and reversal of directional arrows are favorite vandalisms. Theft of stop signs is common and dangerous. Sign theft can be alleviated by using anti-theft hardware. Some maintenance people smear axle grease on the sign posts and backs of the mounting brackets to discourage youngsters. Bullet damage can be minimized by using plastic, plywood or Masonite sign blanks. Evidence of vandalism must be identified and corrected immediately. All public employees should be instructed to watch for and to report vandalized signs. Before replacing any sign in the field, consideration must be given to the need for that sign. Very often, a sign may have been installed for political reasons and serves no real function. These unneeded signs should not be replaced. Necessary signs should be routinely inspected for blockage by vegetation, commercial signs, other traffic signs or a fixed object. Vegetation should be removed. Commercial signs which either physically block traffic signs or which block them by lighting glare at night should be removed. If one traffic sign is blocking another, the one of lesser importance should be relocated. If a sign is blocked by a fixed object, relocate the sign. Traffic signalization is the most complex of all traffic control devices. Therefore, it requires special attention in the maintenance program. The traffic signal assembly consists of several unique components. The signal heads. The masked arm. The post or pole. The controller. The detector loops. The signal lamp should be replaced on a gang basis for economic reasons. Replacing each bulb as it burns out costs about $36 including labor and equipment. Replacing all the lamps in the intersection at one time after 90% or so of the expected bulb life is gone reduces this cost to about $24 per lamp. Not only does replacing all the lamps at one time save an average of $12 per lamp, but it also saves maintenance crew time that can be spent elsewhere and it cuts down on motorist aggravation at having an intersection obstructed. The span wire should be checked to make certain that all fittings are tight and that the wires are not noticeably worn from swaying in the wind or from aging. The assembly should be cleaned each time the signal head is open. Be sure to check the drip loop on the cable entering the signal head. Without the drip loop, water could run directly into the signal head. Dust should be removed from the reflector. The lens should be wiped and the seal around the lens should be checked to see that it is still flexible. Just as with the span wire supported traffic signal, the connections from the mast arm to the signal head and from the mast arm to the pole should be checked for signs of fatigue. The pole should be checked for damage due to impact or weathering. A check of the foundation to make certain it has not shifted should be routine. It is always a good idea to check for exposed wire at the base of the pole. The pole should be grounded to ensure the safety of maintenance personnel and the public. Keep an eye out for vandalism damage and impact damage to the controller cabinet. The detector should be checked for evidence of exposed wire. The controller must also be fully grounded. The resistance to ground should be measured on frequent occasions to ensure that adequate ground exists at all times. Filters, if present, should be changed regularly. Records of all maintenance activities at the intersection must be kept. These records are used for maintenance scheduling and, almost without exception, for legal processes in relation to accidents at the intersection. Signs, signals and markings are all used at intersections in work zones and at railroad grade crossings. They work together to provide a safe operating environment for the motorist. Intersection elements must be visible to the motorist to be safe. Islands, channelizing elements and pedestrian crosswalks are all important to safety. Curbs can be repainted to increase their visibility. And lane lines can be renewed to make the system safer and more efficient. Work zones represent a break in continuity of the roadway from the motorist's point of view. Greater care must be used in communicating changes to the driver for the safety of the crew as well as the driver. Flagging should be correct and precise. The messages should follow the geometric situation. The pavement markings should be free of dirt and debris. All electronic communications devices, like changeable message signs, must be in good working order. This is particularly true of steady burning delineation lights used to guide the motorist around a potentially dangerous area. Grade crossings represent a changed operating environment. And due to the low frequency of trains in most areas, the presence of a train is unexpected by the motorist. Advanced warning is required and pavement markings must also be in place. Coordination with signals that are located nearby is also essential to safety. Failure to coordinate railroad signals with nearby traffic signals can result in traffic being stopped on the track as the train approaches. The site triangle and unprotected railroad grade crossings is absolutely critical to the safety of traffic crossing the track. On structures that block the triangle of sight at junctures where a motorist would make a turn onto the tracks, special warning signs must be maintained. The grass and trees must be carefully controlled to be certain the driver can see approaching trains in time to stop. Good communication with the motorist is a smooth interaction of different types of pavement markings, signs, signals and other controlled devices. The effectiveness of this system is only as great as the least effective part of the system. Maintenance not only must repair or replace damaged features, but also must make certain that the various elements of the system fit together into a coherent, understandable unit for the driver.