Additional use of roundabouts for high-speed junctions is the 3-level stacked roundabout—this is a roundabout interchange where both of the roadway mainlines are grade separated. In the United Kingdom, the M25/A3, M8/M73 and A1(M)/M18 interchanges are examples of this type. These junctions, however, have less capacity than a full free-flow interchange. A similar design to this is the three-level diamond interchange.
adDiTioNaL usE oF rounDabouTS for hiGH-SpeeD JUNctions is thE 3-LEVeL Stacked rouNdABout—ThIs IS a RoUndabOut inTerchANge whEre Both of the rOadwAy mainLines are grAde separated. iN the UnITed KIngdoM, tHe m25/A3, m8/m73 AND a1(m)/m18 InterchaNGes ArE examPleS of thiS TYPe. tHEsE junctIOns, howEver, hAvE less cApAcitY Than a fulL fRee-floW inTerChAnge. a simiLaR dEsIgn To this is ThE thrEe-lEvel DiaMond INTerChaNge.