Paper read before the Rood and Building Moteriols Group of the Society on October 23, I935
THE PROBLEM With ever-incrciisiiig motor traffic i n t Iic litst fctw p r s , tlic dniigcr of skidtling 011 roads I i i i ~ bcconic ii niiicli disciisscd probleni. It-is descrviiig of notice, Iio\ve~r, t,liiit t,lie pcrccntcigc of i i l l t h itcciclttlits on tlic r o d cili~s~tl hy skitlcling is sniiiIl, tlic stiit.ist.ic:il tl~itii viirying hctwccii lo/, rind 5%.
skidding " is i n gcncriil ineiint. the sliding iiiovcnicnt of a wlicel instend of, or i n iitlditioii to, :I rolling niovcnicnt4 : tliis sliding niov~nient intcrcsts iis spcciiilly if it tiikcs pliicc i n a direction iit riglit ;inglcs to tlic plnnc of thc \vliecl. 'l'liis slitling iiiownicnt will tiikc pliice if tlic Iiori~oiitiil forcc csertcd 113' tlic cnr on thc wliecl bcconics greater tlirin tlic friction I)ct\vecii the \vliccl nntl tlic rontl. 'l'his friction is eqiiiil to t,lie product of tlic norniiil forcc witJi which \vliccl iintl roiitl :ire ~)resscd togetlicr ;ind tlic cocfiicicnt of friction. Both factors slionld, tlicrcforc, bc snhjectcd to study.
'l'lic fornicr factor is n coniplicnted function of, iiIiio1ig otlicr bliings, tlic build of t.lic ciir, tlicii of pronoiinced iiIic'cIincss in tlic road, illid t l i c ~f o r c docs not lcntl itself vcryrendily to Iiilioriitory csiimiliiltion ; tlic cocllicicnt of friction ciiti bc scrutinized on n rctliiccd scnle. i\n ntlviintngc is tlint i n tlic Inboriitory one can niiikc i n n simple wiy tlic contlition of tlic siiniplc roiicl surfiicc ~v l i r i t one plcnscs. Thc possiblc occiirrcncc of low coellicients of friction for irlStiiIiCC, niny 1)rolmbly I)c inwstigiitctl on : L Inborntory scnle. llcnsiircincnts of thc coclficicnt of friction on t,lic rond linre I)ccri iniitlc hy scrcrnl inwstipiitors ; I S c h e m a k coefficients o f fiiction in l3y fig / 1 re/ation to ve/oci& 0 Velocity niny nicntion Uriitllcy i n 16nglnnd, Noycr i i n d Stiiisoii in Aincricii , I3outtcvillc i n Priincc, Sclionli, Ncii niii 1111, ctc. in C4crniiiny. TI10 concli~sions t h y arrive a t arc, roiiglily, ti8 follows :