This mod fixes the missing road in Primm, i fixed it by duplicating the road.
Mod problem is Mission Mojave and YUP
The problem is explained in the comments

Quoted from SandBox6
"I can explain this one, as it was kinda my fault...
There are two pieces of road that occupy the same space, which causes clipping under certain lighting conditions.
MMUE disables one piece, and YUP disables the other, so if you use both you end up with no road at all.
It will get updated in YUP so it disables the same one as MMUE, eventually."

Only use if this section is missing
Do not use this fix if you have no problem with this section of the road

My Load Order

FalloutNV.esm
DeadMoney.esm
HonestHearts.esm
OldWorldBlues.esm
LonesomeRoad.esm
GunRunnersArsenal.esm
ClassicPack.esm
MercenaryPack.esm
TribalPack.esm
CaravanPack.esm
YUP - Base Game + All DLC.esm
FreesideOpen.esm
ELECTRO-CITY - CompletedWorkorders.esm
rePopulated Wasteland.esm
AWorldOfPain(Preview).esm
NVInteriors_Core.esm
NVInteriors_WastelandEditonAWOP.esm
AWOPDeadMoney.esm
Momod.esm
Project Nevada - Core.esm
Project Nevada - Equipment.esm
ELECTRO-CITY - Highways and Byways.esm
Project Nevada - Rebalance.esp
CFWNV.esm
The New Bison Steve Hotel.esm
Project Nevada - Cyberware.esp
Project Nevada - Extra Options.esm
SomeguySeries.esm
Niner.esm
YUP - NPC Fixes (Base Game + All DLC).esp
AWOP Interior Music.esp
Mission Mojave - Ultimate Edition.esp
FreesideOpenPatch.esp
Project Nevada - Rebalance Complete.esp
Project Nevada - All DLC.esp
EVE FNV - ALL DLC.esp
MMUE-CP-WMX.esp
CFW-PN-DLC.esp
CFW-PN.esp
CNR_Beta.esp
MMUE-CP-PNEquipment.esp
CFW-DLC.esp
Alternative Start.esp
MMUE-CP-Electrocity.esp
AWOPDeadMoneyVendorPatch.esp
AWOP DLC + GRA Conflict Error Fixes.esp
PipBoyLight.esp
MMUE-CP-PNALLDLC.esp
NewVegasBounties.esp
NewVegasBountiesII.esp
Tutorial Killer.esp
MMUE-CP-PNCore.esp
MMUE-CP-PNRebalance.esp
AWOP-MoMod.esp
AWOPFSOPatch.esp
FSOmusic.esp
Project Nevada - Cyberware Additions.esp
Project Nevada - WMX.esp
Project Nevada - WME.esp
The Mod Configuration Menu.esp
The Weapon Mod Menu.esp
Mojave Nights.esp
NCR Rearmament v1.5 (Lore).esp
hunter.esp
Delay DLC - DM + HH + OWB + LR + GRA.esp
Tutorial Killer - Factions.esp
Tutorial Killer - Project Nevada.esp
Integration - Couriers Stash.esp
LFox Bottle That Water.esp
CASM with MCM.esp
RWD-NV v1.3 [Alternative Version].esp
BuildableBotsNV.esp
NVBabyDeathclawCommander.esp
MoreNiner.esp
Primm_Highway_Fix.esp