Taking all of the above, I propose a different route, for the more I looked at my research, the more patterns I noticed that did not fit into any one author's work. Indeed, it seemed as if they were nipping at the edges in trying to reconcile various passages of geography and detail. And yet, it comes down to Carthaginian intentions and a few key points that may have been dismissed by earlier authors, not so much as what's been stated, but what can be inferred as well. Begin at the End

The key to the puzzle is where Hannibal exited the Alps and into which tribal lands he entered in Italy. It seems Polybios' Insubres and Livius's Taurini are incompatible, but I believe that idea false. I draw on the following passage of Polybios to explain the difference. "A little while later, after his army had regained its condition, Hannibal learned that the tribe of the Taurini, who lived at the foot of the Alps, had fallen out with the Insubres and were inclined to be suspicious of the Carthaginians." [Polybios, III, 60]

Livius referred to this as a "war" [Livius XXI, 39] and the result was that Hannibal's forces were not attacked as they staggered into the plains of Italy. However, from that passage, Hannibal was not aware of the falling out of the two tribes during the march. As far as he was concerned, every tribe was still friendly, or at least neutral, towards the Carthaginians. And if the two tribes had a falling out, then beforehand, they had at least a neutral stance if not an understanding. However, after he reaches the plain, Hannibal learns this is not the case. The use of the word "inclined" in the translation indicates a change of heart towards the Carthaginians. (Ed. Note: The Greek word used is not inclined however. That means leaning. The word used is unsure and the exact translation was "...and were unsure of the Carthaginian's motivations." This would make perfectly good sense if the Taurini were sure that the Carthaginians and Insubres were teaming up to conquer them.)

Do not forget Magilus and the other Gallic chieftains. Nothing is mentioned of them past the Rhone River speech, but as they were received as guides, envoys, and even allies, so they may have continued on with the Carthaginian army. Whether they made the entire trip is open to speculation.

And finally, just as Polybios interjects a diatribe against historians attributing Hannibal's crossing to gods leading him by the hand over the mountains, so Livius injects a vitriolic condemnation of historians who claim Hannibal used the Pennine Alps or Northern Alps passes. He specifically mentions Hannibal did not enter the Salassi tribal lands (just north of the Insubres), and specifically says Hannibal entered the lands of the Taurini.

Strabo mentions four passes in particular that were known at the time of Polybios. However, one can reasonably sure the locals knew a whole lot more of them. Some are more or less passable to an army compared to a single traveler, but the Alps contains more than four--or five if you use Varro's list.

The placement in the list is important. Both place the pass in a more southern area, between the coast road pass and the St. Bernard passes. Whether or not the words "Hannibal's Pass" or "Pass Used by Hannibal" were really in the original text may be a stretch, but considering that Hannibal appeared like a "thunderbolt" from the Alps to the Roman historian Florus, and that Juvenal tells of Hannibal's exploits being the stuff of "speech-day recitations" (Satires, X), it would not be out of line to consider tagging Hannibal's name to a pass. This is balanced by regarding such tagging as over-enthusiasm. Still, it places the passes towards the southern end of the Alps nearer the coastal road than Bernard's passes of the Alps. This not only limits the number of passes, it presents an starting point to consider. How was Hannibal going to get to the Taurini?

Intentions

From a strategic perspective, Hannibal tried to break into Italy and take the war to the Romans. He harbored the idea, confirmed with pre-invasion intelligence, that Gallic tribes hated the Romans and would join his quest to defeat Rome. Hannibal's version of a strategic victory would be to force Rome to the bargaining table and overturn the First Punic War terms. Carthage, and not Rome, would become the pre-eminent military power in the Western Med.

(Ed. Note. While I believe this is admirable speculation, Hannibal's intention only wanted to cripple Rome. He had to know he could not defeat her one on one. He did not have the manpower. He planned to remove her allies. For this to happen it is apparent in every step Hannibal takes, he is planning for a protracted war. Interestingly, this was the same strategy that the Socii wished to carry out in the Social War.

This plan was obvious, and followed Greek thinking of the age. By breaking up the Roman alliance, Hannibal would institute a Italian alliance, to watch Rome, much like Megalopolis was built by the Messians to watch the Spartans. As being the military power in the Mare Nostrum, Hannibal's City simply wanted non-Roman interference in trade. In fact if Rome had given this in the first place, there would not have a first Punic war. The third Punic War was started only because Cato saw that a reviving trade rival in Carthage meant reduced markets for Rome.)

Author response: If Rome lost most or all her Italian allies, Carthage would become pre-eminent and have a free hand in the region.

He may have entertained notions, perhaps beforehand and certainly as he marched up and down the peninsula, that military victories could separate Rome from its allies. That most territories stayed loyal to Rome would not be known to him for years, but his plan hinged on finding allies in Italy, as he could not bring an overwhelming force with him from Spain.

Not all tribes would be so inclined at the start, and thus he needed to pave the way for the march through diplomacy. Again, his envoys returned with a positive response. He would receive guides (Magilus and other chieftains) to show him the way to reach Italy. Yet there were two stumbling blocks: the city of Massilia and the Roman army he knew was coming.

Massilia he could detour around, in part to avoid the idea of a siege, and in part to avoid allowing Rome's allies intelligence on his whereabouts. The idea of hiding a 50,000-man army seems inconceivable today, but given the distance and wild nature of the terrain, it is not too much of an absurd idea to at least be able to move well past Massilia before the Romans could receive word. And it succeeded. The Roman commanders seemed surprised when they discovered Hannibal was north of the Ebro River--and they were certainly analyzing the situation on a day to day basis.

The Roman army would be a different matter. Just as he could not be bogged down with a siege of Massilia, so he could not be intercepted by a Roman army. If he was to break the fabric of the Roman republic and its allies, he had to take the war to Italy.

As it turns out, the two armies did not know each other's location though they were roughly 80km apart, but they did find out fast. Hannibal, being a competent commander, would have taken such scouting and reaction into account during the planning stage.

Hannibal probably planned to bypass Massilia, leaving a rearguard if necessary to prevent scouts from following, and head up the Durance River Valley for a bit, then cut eastward and skirt the Alps to the south, eventually crossing at the Col de Lombard, or perhaps further north at the Col de Larche. Both lead into the Taurini lands. This would be far enough away from the coast road to escape detection, and yet, it is a fairly straight line into Italy.

This is entirely speculation about the route planned but not taken. A couple points serve to make this a credible invasion route.

The Way of Hercules, an ancient path, was a well-known route through the Alps. If Hannibal was trying to get to the Boii, Taurini or Insubres by the quickest route without using the coast road, this would be it.

If envoy/guide chieftains from allied tribes were heading west to reach Hannibal, they would not be wandering the mid to northern Alps, they'd be taking a direct line, too. If they did wander across at mid-Alps, then they would have been prepared to guide Hannibal when he was forced north up the Rhone Valley. However, Hannibal used guides from Brancus and also accepted guides a little later on from the treacherous tribe that led them into an ambush just below the Pass.

It would seem they did not know about the middle Alpine Passes at all--Mont Genevre, Mont Cenis, Col du Clapier--or the Northern ones of the St. Bernards. Otherwise, they would have led Hannibal's army there during the march. No credit is given to Magilus and his chieftains as guides, but both Livius and Polybios mention other guides during the narrative.

Hannibal Crosses the Alps A Route Examined and a Proposed Alternate Route

Introduction
The Sources
Hannibal's March: Polybios and Livy
Polybios vs. Livy: Debate Over Details
A New Route Proposed: Begin at the End
A New Route Proposed: Start at the Beginning
A New Route Proposed: Where is the Druentia?
A New Route Proposed: The Pass in the Alps
Aftermath, Conclusion, and Bibliography