Severiano Ballesteros, the dashing 21-year-old Spaniard who finished yesterday's second round of the British Open tied for the lead with Isao Aoki and Ben Crenshaw, strode to the 17th tee of the Old Course at St. Andrews leading by two strokes.

This is the celebrated "Road Hole" - a menacingly bunkered, 461-yard dogleg to the right, over the flagstone and cement Old Course Hotel, that has humbled the most accomplished golfers.

It has become as much a personality of this fascinating 107th British Open as any of the 156 players. The 17th has inflicted a fearsome number of bogey 5s and worse, embellishing its already ample legend.

Ballesteros, whose charisma and untamable flair for the adventuresome shot have earned him the reputatation as the Arnold Palmer of Europe, was true to his general inclination when he got to the "Road Hole."

A lad who dreams of the impossible, and achieves it frequently enough to replenish his spirit, he shunned safety and went for the potentially most rewarding drive - a massive fade over the hotel garden that might give access to the unseen green with a good second shot.

But, as Palmer had done in similar circumstances five hours earlier, Ballesteros pushed his drive too far right, toward the gravel path road and stone wall waiting there to punish those who are brave but less than precise with their drivers.

Ballesteros nearly hit a pub called Jigger Inn and, like Palmer, got a two-stroke penalty for being out of bounds.

Unlike Palmer, who hooked his second drive into the rough and saw the lead he held briefly during the afternoon disintegrate in a striple bogey. Ballesteros played his second ball at the "Road Hole" magnificently.

He nailed a perfect 270-yard tee shot and got down in four the second time around. But his errant first drive cost him exclusive possession of the halfway lead.

Ballesteros finished the day with a two-under-par 70 and a 36-hole total of 139, five under par. That put him in a three-way tie with first-round leader Aoki of Japan (68-71) and the American, Crenshaw (70-69), both of whom saved pars at the "Road Hole."

Aoki, 35, a former caddy who has won 22 tournaments in Japan during a 14-year professional career, was through the green and in the road after two shots. A wonderful if unorthodox putter, he chose to putt instead of chip from the pavement and rolled up a three-foot embankment and down the sloping green to within a yard of the pin.

Crenshaw, playing in the same threesome, put his second shot on 17 beyond the hole and to the left; the treacherous road bunker precluded a direct line to the flag stick.

Crenshaw, a student of golf history who reverses St. Andrews as the birthplace of the game and one of its finest links, chipped to the left of the hole and sank a lovely 25-foot downhill putt.

One stroke behind the leaders were Australian Bob Shearer (71-69), who two-putted two holes from inside five feet, and the inevitable British Open "phanthom." In this case he was Garry Cullen (73-67), the son of an English game warden, who grew up in Kenya and now lives Nairboi.

At 141 were 1975-'77 champion Tom Watson, 1973 champ Tom Weiskopf, Americans Tom Kite and Bob Byman, and two more Japanese, "Jumbo" Ozaki and Tsuneyki Nakajima, whose putting on the tricky, begrudging greens of the Old Course held them in good stead.

Palmer, runner-up in his first British Open at St. Andrews in 1960 and champion in 1961-62, and five-time champion Peter Thompson of Australia were among a cluster of players at 142.

Jack Nicklaus - champion in 1966 and 1970, the last time the Open was played at St. Andrews - remained in comfortable striking range at 143 after a round in which he took 34 putts, leaving 14 of them within six inches of the hole.

An all-time British Open record crowd of 27,891 braved second day of misty, overcast, chilly and calm in the morning, followed by clearing skies, radiant sunshine and a modest but freshening easterly breeze in the afternoon.

Palmer, who said he hit his irons and putted better than he has in some time, but drove worse, was the people's early choice. Ballesteros, who has a similar sparkle in his eyes and the bold playing style of a younger Palmer, stole the show later on.

But there was another star - the 17th hole which exacted tribute from both. It has become the "Jaws" of this Open, a kind of living embodiment of danger with a character all its own.

In the opening round, there were no birdies at the "Road Hole," and two-thirds of the players took a bogey or worse there. Yesterday there were four birdies, but several of the leaders came to grief at Ozako and Kite with double bogies and Shearer, Cullen and Weiskopf with bogies.

The 17th at St. Andrews is probably a more difficult hole than the 18th at Cherry Hills in Denver, mover which so much fuss was made during last month's U.S. Open. "The drive is tougher at Cherry Hills, but the second shot here is almost impossible," said Palmer. "I'd say there is a harder hole over all."

With the pin cut far to the back, as it has been for two days, there is no safe second shot to the green. To the right is the road.To the left is the road bunker. The only safe way is to lay up short on the right side of the narrow fairway, pitch to the front of the green and try to run a chip close enough to the hole to get down in one butt.

"I think maybe it is the most difficult hole I have ever seen," said Ballesteros. "I think maybe one day, they won't put the hole on the green. They like impossible positions."

Ballesteros, driving superbly, had admirably avoided the 110th bunker that gives the Old Course so much hazardous charm. He drove the 342-yard 10th hole, named "Bobby Jones," and took two putts from 15 feet for his three, the fourth birdie of a round in which he made no putts of more than 10 feet, but never three-putted.

Aoki took the three putts from 16 feet, but made 20-footers for birdies on the fifth and 10th, and another to save par at the 12th. He thought that was the most important shot of his round, more so than the improbable putt from the road.

"He's got a funny of way putting - heel down and toe up - but he sure makes a lot of them," said Crenshaw, who played a solid round and didn't take a bogey.

"He's a very funny guy, very enjoyable to play with. He takes a little of the pressure off," Crenshaw continued. "Every time he went by a bunker, for example, he talked to it. He'd say, 'No thank you, bunker.'"

The flamboyant, immensely popular Ballestaros didn't talk to any bunkers, but he told him self where he wanted to hit his drive on the "Road Hole."

"Straight at the hotel," he said. "If he had made the shot as he envisioned it in his adventure-loving mind he would be the leader of the British Open.