Cat's eye (road)

In the United Kingdom, different colours of cat's eyes are used to denote different situations:

• White is used to indicate the centre line of a single carriageway road or the lane markings of a dual carriageway.[lower-alpha 1]
• Red and amber cat's eyes denote lines that should not be crossed. Red is used for the left side of a dual carriageway, while amber is used for the right side of a dual carriageway.
• Green indicates a line that may be crossed, such as a slip road or lay-by.[9]

These units are not very visible in daylight and are generally used in conjunction with traditionally painted lines. Temporary cat's eyes with just a reflective strip are often used during motorway repair work. These are typically day glow green/yellow so they are easily visible in daylight as well as in darkness, they can then be used on their own for lane division.

Also seen during motorway repair work are plastic traffic pillars that are inserted into the socket of a retractable cat's eye rather than being free-standing. These are often used in conjunction with two rows of the temporary cat's eyes to divide traffic moving in opposite directions during motorway roadworks.

Solar-powered cat's eyes known as solar road studs and showing a red or amber LED to traffic, have been introduced on roads regarded as particularly dangerous at locations throughout the world.[10][11] However, shortly after one such installation in Essex in the autumn of 2006 the BBC reported that the devices, which flash at an almost imperceptibly fast rate of 100 times a second, could possibly set off epileptic fits and the Highways Agency had suspended the programme.[12] The suspension appeared to have been lifted by 2015, when LED cat's eyes began to be installed along newly re-paved sections of the A1 and A1(M) in County Durham and Tyne and Wear.

Flashing blue LED cat's eyes were demonstrated on the TV show Accident Black Spot, aired on Channel 4 on 19 December 2000, which alert the driver to potential ice on the road when a low enough temperature, provisionally set at 3 °C (37 °F), is reached. Proposed enhancements in 2013 were to change the standard white light to amber for four seconds after the passing of a vehicle, or red if the following vehicle is too close or traffic ahead is stationary.[13]

M9 motorway in Carlow, Ireland, with cat's eyes on the road surface and retroreflectors on barriers

In Ireland yellow cat's eyes are used on all hard shoulders, including motorways (neither red nor blue cat's eyes are used). In addition, standalone reflector batons are often used on the verge of Irish roads. Green cat's eyes are used to alert motorists to upcoming junctions. There are limited installations of actively powered cats eyes, which flash white light, on particularly dangerous sections of road such as the single carriageway sections of the N11.

Botts' dots (research started 1953, compulsory in California from 1966) and other raised carriageway markers perform a similar function in areas of the United States that receive little snowfall. In areas of the US receiving substantial accumulating snowfall that requires the use of snow removal equipment, recessed markers or those encased in protective metal are frequently used.[14]

In New Zealand, roads are generally marked with both Botts' dots and cat's eyes (typically there is one cat's eye followed by three Botts' dots places in every ten-metre stretch of highway). The colour pattern on New Zealand roads is white or yellow cat's eyes along the centre of the road (yellow indicating overtaking is not permitted) and red dots along the hard shoulder or left edge of a motorway. Single blue cat's eyes are used to indicate the location of fire hydrants, and green cat's eyes are used to mark the edge of culverts. In rural settings and along State Highways, these markings are augmented by retroreflective posts along the edge of the road (white reflectors on the left, yellow reflectors on the right). Bridges are similarly marked with retroreflective markings in diagonal bands of white and black (to the left) and yellow and black (to the right).[15]

Road-mounted yellow cat's eyes mark road works (Germany)

By contrast to the UK where use of cat's eyes is widespread, in Continental Europe, cat's eyes are almost completely absent as a permanent fixture. Some road users, especially cyclists and motorcyclists, consider cat's eyes unnecessary as an additional lane or position marking identification and actually pose a threat to safety upon impact due to their prominent, slippery and unforgiving nature – particularly in the wet – and of their propensity to be located in close proximity to areas of increased hazard. It is also suggested that the additional emphasis of an already brightly visible and reflective painted lane marking is simply not required for any potential road event or condition. Many also consider that the absence of cat's eyes reduces the risk of physical and audible discomfort when driving, and that their benefits to safety are exaggerated.

In Lebanon, cat's eyes are widely used on most freeways, highways and roadways. On freeways and highways, every one (or sometimes two) white stripes separating lanes is followed by a white shining cat's eye. On the edge of the road next to the median strip, a yellow cat's eye is placed every 10 metres (33 ft). On the road shoulders a red shining cat's eye is placed every 10 metres (33 ft). On roadways separated by double yellow lines, a yellow cat's eye is placed inside the double yellow lines every 10 metres (33 ft). Before speed bumps, a series of cat's eyes are placed shining white to the oncoming traffic and red to the car from the opposite direction. On pedestrian crossings, blue shining cat's eyes are placed after every zebra line. On roads with traffic lights, a series of red shining cat's eyes are placed 50 metres (160 ft) before traffic lights to make drivers slow down.