0 ▁years ▁after ▁the ▁first ▁formal ▁studies ▁had ▁been ▁prepared . ▁The ▁final ▁cost ▁of ▁the ▁whole ▁scheme ▁including ▁fe eder ▁roads ▁and ▁not ▁just ▁the ▁tunnel ▁itself ▁was ▁IR £ 1 0 5 ▁million ▁( approx ▁€ 1 3 3 ▁million ). ▁The ▁tunnel ▁has ▁two ▁separate ▁two - lane ▁b ores ▁( each ▁l ane ▁ 3 . 7 5 ▁m ▁wide ). ▁There ▁is ▁a ▁service ▁walk way ▁about ▁ 1 ▁met re ▁across ▁which ▁doubles ▁as ▁an ▁emer gency ▁escape . ▁During ▁periods ▁of ▁maintenance , ▁one ▁t ube ▁may ▁be ▁closed ▁and ▁the ▁other ▁used ▁for ▁bi - direction al ▁traffic . ▁The ▁environment ▁within ▁the ▁tunnel ▁is ▁controlled ▁by ▁a ▁closed ▁circuit ▁TV , ▁traffic ▁control ▁and ▁Super vis ory ▁Control ▁and ▁Data ▁Ac quisition ▁( SC AD A ) ▁system . ▁External ▁phot oc ells ▁linked ▁to ▁the ▁SC AD A ▁system ▁provide ▁a ▁level ▁of ▁tunnel ▁light ing ▁most ▁compatible ▁with ▁ambient ▁light ▁levels ▁outside . ▁To ▁assist ▁drivers ▁in ▁adjust ing ▁their ▁eyes , ▁light ing ▁gradually ▁bright ens ▁as ▁they ▁approach ▁an ▁exit . ▁ ▁Jet ▁fans ▁located ▁within ▁nich es ▁in ▁the ▁roof ▁of ▁the ▁imm ers ed ▁t ube ▁sections ▁provide ▁longitud inal ▁vent ilation , ▁and ▁the ▁tunnel ▁is ▁equ ipped ▁with ▁fire ▁and ▁life ▁safety ▁equipment . ▁ ▁Despite ▁the ▁cost ▁of ▁its ▁construction ▁and ▁operation ▁the ▁tunnel ▁is ▁not ▁to l led . ▁The ▁Fe as ibility ▁Study ▁for ▁the ▁tunnel ▁en vis aged ▁that ▁the ▁crossing ▁could