Also known as "Cycling Road," Routes #16, #17 and #18 are a favorite hangout for bicyclists and motorcyclists alike. It just so happens that many of these two-wheeling enthusiasts are Pokémon trainers as well, and you must fight your way down the long slope to Fuchsia City. Once there, you will have a chance to visit the Safari Zone.
Before you head past the guard post, dig your Cut-trained Pokémon out of the computer in Celadon City and use him to snip away at the tree blocking the northern part of Route #16. It's here that you'll find the patch of wild grass that is your first chance to catch a Doduo, as well as a secret house containing HM 02, Fly. Use this to teleport to any city you've visited, or for a two-turn Flying-type attack that is similar to Dig.
#143 Snorlax
#84 Doduo
You won't get far in Route 16 without defeating the giant, sleeping Snorlax blocking your path. To wake him up, use your flute, and then defend yourself against his grumpy level 30 Snorlax rage.
There's only one more Snorlax in the game (at Route #12), so capture him now! He'll learn some okay attacks at level 35 and beyond, but for now he's mainly defensive. He has a ton of Hit Points, comes with Rest, and wakes from it quickly.
The problem with Fly is that it requires a Flying-type Pokémon. And while Fly itself is a very useful skill, you won't get any Flyer worth adding to your party (like Aerodactyl) for a little while. So you'll want to pick up a disposable flying Pokémon for the time being... Like Doduo!
Doduo, which can be caught in any version, is by no means terrible. Drill Peck is a strong attack that's great against the many Fighting-type Pokémon in this area (as well as more seldom-seen Grass and Bug Pokémon), but there's not a whole lot else to get excited about. The evolved form, Dodrio, which can be caught in Route #17 in Yellow only (or raised at level 31 in any version) is a fairly speedy, strong attacker that can do good damage with Normal skills like Tri Attack.
Route #17's brutal slope drags you downward unless you hold the or buttons to steady yourself. But there's no reason not to speed to the bottom, since the only thing of interest here is the Ponyta in Yellow. (Although there are some pretty useful hidden items -- five in total -- if you're willing to stick around and fiddle with the Itemfinder for a while). When you get to Route #18, don't miss the trader in the top floor of the guard post.
1
Biker
560
Weezing
LV28
Koffing
LV28
Weezing
LV28
2
Cue Ball
725
Machop
LV29
Machoke
LV29
3
Cue Ball
725
Mankey
LV29
Primeape
LV29
4
Biker
660
Muk
LV33
5
Biker
580
Voltorb
LV29
Voltorb
LV29
6
Cue Ball
825
Machoke
LV33
7
Cue Ball
650
Mankey
LV26
Mankey
LV26
Machoke
LV26
Machop
LV26
8
Cue Ball
725
Primeape
LV29
Machoke
LV29
9
Biker
580
Weezing
LV29
Muk
LV29
A
Biker
500
Koffing
LV25
Weezing
LV25
Koffing
LV25
Koffing
LV25
Weezing
LV25
Route #16 encounters
Rattata
30%
30%
25%
Raticate
5%
5%
5%
Spearow
40%
40%
30%
Fearow
N/A
N/A
5%
Doduo
25%
25%
35%
Route #17 encounters
Raticate
30%
30%
N/A
Spearow
40%
40%
30%
Fearow
5%
5%
20%
Ponyta
N/A
N/A
24%
Doduo
25%
25%
25%
Dodrio
N/A
N/A
1%
#77 Ponyta
Yellow missed out on the early Growlithe and Vulpix in Blue and Red (unless you count the Vulpix you could win from the Game Corner), but now it finally gets its first Fire Pokémon since Charmander: Ponyta.
Ponyta doesn't get the greatest skills... For Fire, it's just Ember for starters and Fire Spin at level 39. But the saving grace of Ponyta and its evolved form, Rapidash, is their incredible Speed, making them easily the fastest of the Fire Pokémon.
#108 Lickitung
If you're collecting all of the Pokémon, the guard post in Route #18 is a great opportunity for Red/Blue players to trade a Slowbro, something you can fish up fairly easily, for a rare Lickitung. But if it's utility that interests you, you're better off keeping the Slowbro. Lickitung is a hearty fellow, but his array of Normal attacks are poor. Yellow players can only trade a rare Tangela for a common Parasect: a truly bad deal.
Almost to Fuchsia City
Just before you arrive at Fuchsia City via Route #18, you will find three Bird Keepers waiting for you on the other side of the guard house. With the help of one little Electric Pokémon (you know the one), you can make short work of all three in no time.
580
or 
buttons to steady yourself. But there's no reason not to speed to the bottom, since the only thing of interest here is the Ponyta in Yellow. (Although there are some pretty useful hidden items -- five in total -- if you're willing to stick around and fiddle with the Itemfinder for a while). When you get to Route #18, don't miss the trader in the top floor of the guard post.
Raticate
Fearow
Ponyta
Dodrio
Magikarp
Goldeen
