Abstract:Ｔｏday, tｒaffｉc lights installed ｏn ｔhｅ ｃrｏssing at
all， ｔｏ ｅaｓｅ ｔhe trａｆfic ｏf ｖehicles has become thｅ mos
ｔ coｍmｏn ａnｄ most efｆeｃtive meanｓ。 Ｓoｃial ｄｅveｌopｍｅｎ
ｔ, pｅopｌe'ｓ cｏｎsumｐtioｎ ｌｅｖels continｕｅ ｔo incrｅase,
pｒｉvate veｈicles iｓ increasing。 Oｆ peoｐlｅ， caｒs and more ro
ａds have ｌess trafｆｉc staｔｕｓ iｓ obvious。 Ｔｈerｅｆorｅ, tｈｅ
adoption of efｆective methodｓ to coｎtrｏl traffic ｌｉghtｓ is imp
ｅｒａｔｉｖe. PLＣ intelｌigent control pｒiｎcｉpｌe ｉｓ ｔhe cｏr
ｅ of the controｌ ｓyｓtｅｍ usiｎg PLC ｎortｈ—south dｉrection t
ｏ eaｓt-wｅｓt directｉon or scalｅ ｏｆ the ｖehiｃｌe ｂy the ｎ
umber ｏf sub-fｉｌｅ， the apｐｒｏｐrｉate ｔｈing given ｔhe gｒ
een light nｏrｔh-souｔh ｄiｒectｉon and lengtｈ of ｔｉme iｓ alｓ
ｏ sub—ｆｉle aｃcｏrｄiｎｇ to ｃeｒtaiｎ rules。 Tｈis ｓcａle caｎ
be achieved gｉvｅn the greeｎ ligｈt ａt tｒaｆfiｃ ｄuratｉｏn, to ａ
chieve ｍaｘiｍum reｌeａsｅ a cａｒ to rｅdｕcｅ ｔhe staｇnａtiｏ
ｎ oｆ ｖehｉcles croｓsｉｎｇ ｔo ｅaｓｅ ｔrafｆic ｃonｇeｓtion，
tｏ achｉeve opｔimal coｎｔroｌ, thus imprｏvｉng tｈe ｅfficiｅｎ
cy of ｔｒafｆic conｔrol sｙstem.
PLC strucｔuｒe is simplｅ， easy ｐroｇｒａmmｉng, ｈigｈ ｒｅ
liability， haｓ ｂeｅｎ wｉdely ｕseｄ ｆor ｉnｄｕstrial process
anｄ ｌｏcaｔion ｏf thｅ ａｕtｏｍatic cｏntｒol。 Ｔhe usｅ ｏf the
PＬC ｈas the cｈarａcteristiｃs of environmenｔａl ａdａptabｉｌity,
whiｌe its inｔernaｌ ｔimer ｒesｏuｒceｓ ａre ｖeｒy riｃh， thｅ
cｕｒｒｅnｔ wｉdesｐread use ｏf the "pｒogreｓｓiｖｅ" sigｎal f
ｏr ｐｒecise contｒol， paｒtｉcuｌarlｙ cｏnｔrol oｆ multｉ-forｋ
can be easily ａｃhieved。 Ｔherefore， the PＬC ｉs now ｉｎcreasingl
ｙ used ｉn ｔraffｉｃ lighｔｓ sysｔem．
ＰLC aｌso hａｓ ａ commｕｎications neｔworkｉng cａpａbilｉｔie
